The reactions of the actors and actresses in some scenes are spontaneous. For example, when the children first enter the Chocolate Room and see the candy gardens, their reactions are real, it was really their first view of that particular set.
The Wonkatania was on a track in the chocolate river, but the actor playing the Oompa Loompa at the helm thought he was actually steering it. For the sake of believability, Director Mel Stuart didn't tell him the truth.
After reading the script, Gene Wilder said he would take the role of Willy Wonka under one condition: that he would be allowed to limp, then suddenly somersault in the scene when he first meets the children. When Director Mel Stuart asked why, Gene Wilder replied that having Wonka do this meant that "from that time on, no one will know if I'm lying or telling the truth." Stuart asked, "If I say no, you won't do the picture?" and Gene Wilder said, "I'm afraid that's the truth."
Ernst Ziegler, who played Grandpa George, was nearly blind (from poison gas in World War I), so he was instructed to look for a red light to guide him when his character was meant to be looking in a certain direction.
Even Julie Dawn Cole (Veruca) was fooled by the scene in which Willy limps out of his factory to greet the Golden Ticket winners. She mentions in the DVD commentary that she thought that Gene Wilder had injured his leg for real (and that the filming would have to be temporarily halted because of it). This resulted in her being just as stunned by Willy's somersault as the audience was.
In Willy's office at the end of the movie, Charlie's stunned reaction to the candy maker yelling at him is real. Per Mel Stuart's "Pure Imagination: The Making of Willy Wonka and the Chocolate Factory" Peter Ostrum was not told beforehand that Willy would be yelling at Charlie. Stuart felt that doing it that way would allow for a better, more real, reaction from Charlie. Gene Wilder mentioned in Pure Imagination: The Story of 'Willy Wonka and the Chocolate Factory' (2001) that he wanted more than anything to warn Peter about the yelling beforehand (particularly because the two had become good friends during filming, and Wilder wanted Ostrum to be assured that he was only acting, and that of course he still loved him), but Stuart forbade it.
Gene Wilder's acting during the boat ride sequence was so convincing that it frightened some of the other actors and actresses, including Denise Nickerson (Violet). They thought that Wilder really was going mad from being in the tunnel.
During the "Wonka Wash" car scene, the foam used to spurt out was compiled from basic fire extinguishers, but what was unknown to the cast and crew was that the foam itself was a potent skin irritant, so after shooting the scene, the actors and actresses were left in considerable discomfort when their skin puffed up and required several days to receive medical treatment and recovery.
Peter Ostrum (Charlie Bucket) made no other films. He turned down a five picture contract, because he didn't want to make acting his profession. He later became a veterinarian. In fact, out of all of the children in this movie, Julie Dawn Cole (Veruca Salt) is the only one still acting (as of 2013).
Sammy Davis, Jr. expressed an interest in playing Bill, the candy store owner, but the filmmakers deemed it as too kitschy and declined. Furthermore, Mel Stuart didn't like the idea, because he felt that the presence of a big star in the candy store scene would break the reality. Nevertheless, the candy store song, "The Candyman", became a staple of Davis' stage show for many years.
When Willy Wonka drinks from a flower-shaped cup and then eats the cup, the cup itself was made of wax. Gene Wilder had to chew the wax pieces until the end of the take, at which point, he spat them out.
Denise Nickerson had a Violet-esque experience in real-life. She said in the DVD commentary that one day in math class, kids started pointing at her and laughing, and one of her friends told her she was turning purple. The make-up that had been used on her for the film had apparently seeped into her pores and started to resurface (which, she jokingly remarks, prevented her from getting any dates at that school).
This movie was shot in Munich, Germany, but the producers had to go outside of Germany to recruit enough little people to play the Oompa Loompas. Many of the people cast as Oompa Loompas (German or otherwise) did not speak English fluently, if at all. This is why some appear to not know the words to songs during the musical numbers.
When asked his thoughts on the 2005 adaptation of Charlie and the Chocolate Factory, Gene Wilder stated that he enjoyed Johnny Depp's performance as Willy Wonka, but disliked the film as a whole, as he was not a fan of Tim Burton as a director, and said he was generally insulted when his films were remade.
Julie Dawn Cole did not know the rock in the chocolate room she was dropping down onto to smash the watermelon-sized chocolate egg was real, and she badly cut her left knee falling onto it. If you watch carefully in her first clip with the egg, you can see her left stocking is bloody. She still has a scar on her knee from the injury.
According to Mel Stuart's book "Pure Imagination: The Making of Willy Wonka and the Chocolate Factory", the reason everything in Willy's office is cut in half was because Stuart couldn't bear the thought of, after having gone through all the whimsical and creative rooms in the factory, ending the movie in an ordinary office. Everything was cut in half to make the room look more Wonka-esque.
In the DVD commentary, Peter Ostrum mentions that, toward the end of the shoot (with him being the only kid left) he and Gene Wilder often ate lunch together. Fittingly, they finished those lunches by sharing a chocolate bar for dessert as they walked back to the set.
It is said Roald Dahl was reportedly so angry with the treatment of his book (mainly stemming from the massive re-write by David Seltzer) that he refused permission for the book's sequel, "Charlie and the Great Glass Elevator", to be filmed. Seltzer had an idea for a new sequel, but legal issues meant that it never got off the ground. Reportedly, Dahl was so unhappy, that he refused to ever watch the completed film in its entirety. Once, while staying in a hotel, he accidentally tuned into a television airing of the movie, but reportedly changed the channel immediately when he realized what he was watching. However, photographic evidence contradicts this: behind-the-scenes footage on the DVD shows him looking happy while visiting the set, and he even attended the premiere. Julie Dawn Cole, commenting in 2011 on these events, remembers him as being a large, scary man.
According to the DVD commentary, Julie Dawn Cole kept several props from the movie (after being instructed not to) including the Golden Ticket, an Everlasting Gobstopper, and a Willy Wonka candy wrapper.
The face in the psychedelic tunnel movie is that of Walon Green, friend of Mel Stuart, and Screenwriter of The Wild Bunch (1969). According to Stuart's memoirs, Green is the only person who would agree to let a centipede crawl on his face for the sake of a children's film.
According to Director Mel Stuart's "Pure Imagination: The Making of Willy Wonka", when Gene Wilder walked in to audition, Stuart knew before he'd even uttered a single word that he had found his Willy Wonka. The audition convinced him even further, so when Wilder finished and left the room, Stuart chased him down the hallway, cut him off at the elevator bank, grabbed his arm and told him "You're doing this picture, no two ways about it! You are Willy Wonka!" Producer David L. Wolper, however, was furious because he hadn't yet had the chance to negotiate a fee.
Before entering the Inventing Room, Willy Wonka gives an introductory speech in German, with an accent, but otherwise phonetically and grammatically correct. It goes "Meine Herrschaften, schenken Sie mir Ihre Aufmerksamkeit. Sie kommen jetzt in den interessantesten und gleichzeitig geheimsten Raum meiner Fabrik. Meine Damen und Herren: der Inventing Room. He even pronounces the German "r" correctly, and says "Inventing Room" with a proper German accent. The speech translates: "Ladies and gentlemen, please give me your attention. You now come into the most interesting room of my factory, the most secret room at the same time. Ladies and gentlemen: the Inventing Room.
Julie Dawn Cole (Veruca Salt) explained in her memoir "I Want it Now!" that the mixing bike in the Inventing Room was initially meant to be pedalled by an Oompa Loompa. When it came time to film the scene, however, it was discovered that none of the Oompa Loompa actors' legs were long enough to reach the pedals. So the filmmakers came up with a creative solution: Gene Wilder would do the pedalling instead, while singing "Sweet Lovers Love the Springtime".
The scene where Augustus Gloop was interviewed for being the first Golden Ticket finder was shot at a real German restaurant. Most of the cast members went there for lunch during the time the movie was being filmed.
Denise Nickerson's blueberry scene was shot in the middle of the day, leaving a time frame in between takes for lunch. She had to stay in her blueberry costume for that duration and had to be turned over several times to keep proper blood circulation.
Mel Stuart initially wanted to reveal that Willy Wonka had strategically placed the Golden Tickets in order to give the factory to Charlie. The idea was dropped, but the hints remained in the fact that Mr. Wilkerson conveniently showed up every time a ticket was uncovered.
Peter Ostrum went through puberty during the film. This is evident as voice is high during the duet of "I've Got a Golden Ticket", and is much deeper later in the film, such as during the bubble scene.
Even though the film didn't do well at the box-office, surprisingly, when it was released to home video, it gained more attention. This was one of the more popular movies for rentals by the time the rental fad took off in the 80s.
During the "Pure Imagination" song, Willy Wonka whips his cane around here and there to stop the crowd in place during various points of the song. According to Paris Themmen (Mike Teevee) in the DVD commentary (at around fifty-three minutes), during one of the takes as Gene Wilder whipped his cane around, he accidentally whacked Themmen. In her memoir "I Want it Now!", Julie Dawn Cole (Veruca Salt) mentioned that she was also accidentally whacked by the cane a couple of times.
The film was originally financed by the Quaker Oats Company, which hoped to tie it to a new candy bar it intended to bring on the market. When the film was released, the company began marketing its Wonka chocolate bars. Unfortunately, an error in the chocolate formula caused the bars to melt too easily, even while on the shelf, and so they were taken off the market. Quaker sold the brand to St. Louis-based Sunline Inc. (which later became part of Nestlé via Rowntree) not long after this. Sunline was able to make the brand a success, and Wonka-branded candy (most of which isn't chocolate-based) was available in the U.S. until the 2010s. Although the novel, on which the movie was based, was called "Charlie and the Chocolate Factory", the movie was renamed to promote this candy tie-in.
Whenever a scene was filmed inside the Buckets' house, Ernst Ziegler (Grandpa George) would take off his shoes and tuck them under the set bed before crawling in to film the scenes. When it came time to film the portion of the "I've Got a Golden Ticket" song that involved Grandpa Joe and Charlie looking under the bed, Director Mel Stuart wanted to move Ziegler's shoes out of the way to film the scene, but Ziegler protested vehemently, as he was afraid they would take his shoes away, and he valued those shoes very much so, as they were his only remaining possession from before World War II. Eventually, Stuart was able to convince Ziegler to allow them to move his shoes to film the scene.
During the construction of Willy's office, in which everything is cut in half, one of the prop men accidentally sawed in half a non-prop coffee pot that someone had put in the work area. Only when coffee began spilling out did he realize his mistake.
Among Wonka's lines are the following quotations: "Is it my soul that calls upon my name?" from William Shakespeare's "Romeo and Juliet"; "All I ask is a tall ship, and a star to steer her by" from the John Masefield poem "Sea Fever"; "A thing of beauty is a joy forever" from John Keats's "Endymion: A Poetic Romance", and "Round the world and home again, that's the sailor's way!" from William Allingham's "Homeward Bound". "We are the music makers..." is from Arthur O'Shaughnessy's "Ode", which also gave us the phrase "movers and shakers". "Where is fancy bred..." and "So shines a good deed..." are from William Shakespeare's "Merchant of Venice". The lines to the song "Sweet lovers love the spring time... " are from Shakespeare's "As You Like It". "Candy is dandy, but liquor is quicker" is from "Reflections on Ice Breaking" by Ogden Nash. "The suspense is terrible, I hope it will last" is a quote from Oscar Wilde's "The Importance of Being Earnest". These literary quotations were not in Roald Dahl's original script. They were added for one reason by David Seltzer when he re-wrote the screenplay.
Peter Ostrum said in the DVD commentary that he and Jack Albertson were very excited to do the Fizzy Lifting Drink scene, thinking it would be a lot of fun, but that it wasn't, due to the metal surrounding them being rather sharp, and the harnesses being extremely tight in the crotch area. Albertson joked that music from Pyotr Ilyich Tchaikovsky's Nutcracker Suite should be played in the background of that scene.
The scene of Violet Beareguarde's demise where she swells up into a blueberry was done in two takes. Take one was pumping air into an inflatable suit, and take two involved stuffing Denise Nickerson into a two-piece Styrofoam cut out. When rolling Denise around in her blueberry suit, the Oompa Loompas had a hard time controlling the rolling actress and would send her crashing into the wall several times (prompting Denise to say in the DVD commentary that the Oompa Loompas didn't have their "blueberry driver's licenses").
Denise Nickerson (Violet Beauregarde) and Julie Dawn Cole (Veruca Salt) had a crush on Peter Ostrum (Charlie Bucket). During filming, the girls would alternate days over which one would spend time with Ostrum. Bob Roe was also an object of attraction for the two. On the day they didn't get to spend with Peter, they would spend it with Bob Roe. Bob Roe was the son of First Assistant Director Jack Roe.
The scene where the technician tries to impress the three businessmen with the large computer to (unsuccessfully) give the results of the (then three) remaining Golden Tickets was the last scene filmed for the movie. It was filmed at such a last minute, that there was a ton of luggage scattered around the set, as the cast and crew were already in the process of packing up to wrap up the movie.
Julie Dawn Cole kept her Everlasting Gobstopper and her Golden Ticket. On the DVD commentary, she admits that she accidentally stole it from the set. Peter Ostrum (Charlie) said he returned it because he was told to. Among other props that Cole kept from the film, was a Scrumdiddlyumptious bar, a Wonka Bar, and a golden egg (which was presented to her as a gift on the day she shot the Golden Geese Room scene which was on her thirteenth birthday). She held on to the golden egg for many years until it spoiled, and inevitably had to discard it. She also sold her Everlasting Gobstopper around the time the Tim Burton remake came out for an undisclosed amount. To this day, she still has a Scrumdiddlyumptious bar and a Wonka Bar. Her Golden Ticket is on display in Sweet Pete's candy store in Jacksonville, Florida.
The scene of Mike's demise was difficult to film. When seen far away while in the television, it was accomplished through bluescreen. While seen in the television from close-up, Paris Themmen (Mike) was standing on a platform on a huge television set. The shot where Mrs. Teevee picks him up was a doll, and the single shot where we see a close-up of Mike dangling from his mom's fingers (at around one hour and thirty minutes) was accomplished by having Paris dangle from a Styrofoam thumb and forefinger covered with fabric.
The idea for adapting the book into a film came about when Mel Stuart's ten-year-old daughter read the book and asked her father to make a film out of it, with "Uncle Dave" (David L. Wolper) producing it. Stuart paid her fifty dollars for the advice.
Despite all the chocolate bars being practically designed for the movie in abundance, very few relics and props of the film survived. Director Mel Stuart explained this regret of not keeping many of the props (as they would be considered highly valuable) citing that at the time of production on a film, no one really knew just how successful it would be.
When climbing aboard the Wonkatania, Grandpa Joe said, "If she's a lady, I'm a Vermicious K'nid". Vermicious K'nids are the shape shifting aliens that invade the Space Hotel USA in Roald Dahl's Charlie and the Great Glass Elevator, the literary sequel to Charlie and the Chocolate Factory.
Peter Ostrum mentioned in the featurette Pure Imagination: The Story of 'Willy Wonka and the Chocolate Factory' (2001) that he was in the sixth grade when he read from the book for the part of Charlie in May 1970, because there wasn't a script. In late July, he went to New York City for a screentest and several weeks later, he was told he had the role, leaving his family ten days to relocate him to Munich for five months.
When interviewed for the 30th Anniversary Special Edition, Gene Wilder stated that he enjoyed working with most of the child actors and actresses, but said that he and the crew had some problems with Paris Themmen, claiming that he was "a handful".
In the featurette Pure Imagination: The Story of 'Willy Wonka and the Chocolate Factory' (2001), Writer David Seltzer and Director Mel Stuart relate that David had left Munich for his vacation cabin in Maine, thinking his contribution to the film was completed when Mel realized that the screenplay ended with Grandpa's line: "Yippie!" Mel phoned Maine from Munich and told David that he couldn't finish the picture without a good ending line. Dave responded with the only thing he could think of, that they are flying in the air, Willy Wonka looks at Charlie and says, in a very warning voice, the "happily ever after" lines.
Veruca Salt's name, also spelled "Verruca" or "Verucca", is a medical term for a wart, usually found on the foot, and caused by a virus. Seems appropriate, considering the character's personality. In the book (as well as the 2005 Tim Burton adaptation), when learning the children's names, Willy Wonka mentions that "verruca" is a wart on the bottom of a foot.
Denise Nickerson and Paris Themmen (in the DVD commentary) cited lines they say in the film that have English inflection, due to time spent around Julie Dawn Cole. (Nickerson's is when she repeats "Everlasting Gobstopper" after Willy Wonka first shows them to the children, and Themmen's is when he asks, "Am I coming in clear" after being sent through television).
The last line from the original script was "Grandpa saying "Yippee!" Mel Stuart was so upset with it, that he had called David Seltzer, who had just left to go on vacation to his fishing cabin in Maine, and demanded he change the last line. There, over the phone, he came up with Willy telling Charlie that the man who got whatever he wanted lived happily ever after.
In the scene where Wonka angrily reads to Charlie and Grandpa Joe the contract out loud, he reads two lines in Latin: "Fax mentis incendium gloriae" and "Memo bis punitor delicatum". The first line roughly translates to "The torch of glory kindles the mind". The second line, as it is heard in the movie, is gibberish. The closest Latin equivalent would be "Memor bis punitor delictum", which translates to "I am mindful (that) the crime is punished twice (or in two ways)."
The town of Nordlingen, Germany, over which the Glass Elevator flies at the end, has a rare distinction. It is located inside a twenty-five kilometer (fifteen and a half mile) wide crater from an asteroid impact of over fourteen million years ago. You can just see the ridges of the crater's edge in the top of the screen (it is not the town wall.) Some stone structures in Nordlingen, and surrounding areas, are speckled with tiny little diamonds from the impact.
The inspiration behind the book came about because as a child, Roald Dahl went to a Cadbury's chocolate factory and he and his classmates were willing guinea pigs for Cadbury's, and would test out new inventions and confectionery creation and it later inspired Dahl to write the story. Dahl told this story in his autobiography "Boy: Tales of Childhood".
Roald Dahl disowned the film, the script of which was partially re-written by David Seltzer after Dahl failed to meet deadlines. Dahl said he was "disappointed" because "he thought it placed too much emphasis on Willy Wonka, and not enough on Charlie", as well as the non-casting of Spike Milligan. He was also "infuriated" by the deviations in the plot Seltzer devised in his draft of the screenplay, including the conversion of Slugworth, a minor character in the book, into a spy (so that the movie could have a villain) and the "fizzy lifting drinks" scene. To add insult to injury, Seltzer had Willy Wonka spout quotations all the time that were not originally in the book. As a result, Dahl refused to sell the company the rights to the book's sequel, "Charlie and the Great Glass Elevator".
While giving interviews as part of the 40th Anniversary celebration of the theatrical release, Denise Nickerson mentioned that, because of all the gum she had to chew as Violet, she ended up with thirteen cavities. The reason is that, although sugarless gum was around in the early 1970s, the formula was a bit different than that of modern sugarless gums, and didn't make very good bubbles. So Denise was stuck chewing regular, sugared gum.
The Tinker quotes from the poem "The Fairies" by William Allingham. "Up the airy mountain, down the rushy glen, we daren't go a hunting, for fear of little men. You see, nobody ever goes in... and nobody ever comes out."
Augustus Gloop (number one on the map) was from Dusselheim, Germany; Violet Beauregarde (number three) was from Miles City, Montana, and Mike Teevee (number four) was from Marble Falls, Arizona. Of these cities, the only one that isn't fictional is Miles City, Montana. Charlie Bucket's and Veruca Salt's hometowns are never mentioned throughout the movie, but it is likely Veruca and her family reside in the UK, especially since number two on the map is over the British Isles. (Mr. Salt tells the workers he will give the one who finds a Golden Ticket a one-pound bonus and there is a sign inside the factory reading "SALT'S: THE PEANUTS OF THE QUEEN!")
The coin, which Charlie found in the gutter, is a Maria Theresa Thaler. This is a silver dollar sized Austrian coin originally minted in 1780, and manufactured almost continuously since then by various mints.
According to the Wonka "kids", the hair and make-up lady, who was German, used a German word to refer to Gene Wilder's often unruly hair, not realizing that the English translation of the word is "chicken".
Gloria Manon, the actress who played the wife in the hostage sequence whose husband Harold is being held hostage for her Wonka bars, also plays the female reporter who interviews Mike Teevee. She is slightly off-camera, but has one line directed toward Mike.
Since this was filmed before the days of CGI, one of the visual effects that needed to be accomplished was Violet turning blue. At the time, the development of color layering was in process. According to the book, Violet's face and hair turns blue. Mel Stuart worked with it, but was only able to turn her face blue. Further development of the color layering was perfected by the time Star Wars: Episode IV - A New Hope (1977) was released and was ready for use to make the light-saber concept look good.
A dummy made up to look like Michael Bollner (Augustus Gloop) was used for the scene where Augustus gets stuck in the pipe, specifically during the long shots of the guests watching him from across the river and when he eventually shoots up the pipe. This is referenced in the audio commentary on the DVD and Blu-ray. A picture of the dummy can even be seen in the "Cast/Crew" section on the 30th Anniversary DVD of Willy Wonka & the Chocolate Factory (1971).
After the company finished filming in Munich, Germany, the studio and locations were then taken over by the Cabaret (1972) people. On the DVD commentary, one of the kids remarked, "We moved out, and Liza Minnelli moved in".
There's been some debate as to the correct spelling of Mike Teevee's last name. In the movie's closing credits, as well as in all of the promotional media for the movie's U.S. release, Mike's last name is spelled "Teevee". In the book, it is spelled "Teavee" and finally, in the movie, during the scene where all the children sign the large contract, Mike is seen signing his name as "Mike T.V.". In the DVD commentary, Paris Themmen said that during the contract signing scene, he was told by Director Mel Stuart to sign his name as "Mike T.V." because it would allow the scene to be filmed quicker.
The scene of Veruca's "demise", was filmed on Julie Dawn Cole's thirteenth birthday, on Monday, October 26th, 1970. Julie Dawn Cole was born on Saturday, October 26th, 1957. In the DVD commentary, she said "no one wished her a happy birthday", and Denise Nickerson starts singing.
Although he is first billed, Gene Wilder (Willy Wonka) does not appear until about twelve minutes and fifty seconds into the film, although he appeared full time from about forty-four minutes until the rest the film's duration. He is however mentioned several times during the first half of the film.
Contrary to popular belief, Fred Astaire was never considered to play Willy Wonka. According to Mel Stuart's book "Pure Imagination: The Making of Willy Wonka", Fred expressed interest in playing the eccentric chocolatier, but that wasn't brought to either Stuart or David L. Wolper's attention. Just as well, because, as Stuart says in his book, he didn't conceive of Willy Wonka as a seventy-two-year-old man, which happened to be what Astaire was at the time.
In the crowd outside the Wonka factory, you can see a crowd member, on-screen left, holding a large professional motion picture camera. There are shots in the movie, of the crowd and the chosen families coming forward, and of the Slugworth figure, which were made by that camera.
The "kids" on the DVD commentary said the child named Winkelman, was played by Mel Stuart's son Peter. The uncredited boy sitting in front of Peter Ostrum in the classroom scenes, is Bobby Roe, son of First Assistant Director Jack Roe, and that the uncredited girl with pigtails in the classroom across the aisle from Peter was played by Madeline Stuart, Mel's daughter. In the featurette "Pure Imagination", Mel mentions his daughter was ten years old in 1970 when she read the book and suggested to him that he approach "Uncle Dave" (David L. Wolper) with the idea of turning the book into a movie.
In the candy shop scene at the beginning, a sign for "Fickelgruber's Fudge" can be seen. In the book Fickelgruber was, along with Slugworth, one of the rival candy makers who sent spies to Wonka's factory.
Verruca Salt was technically the only child not to find a Golden Ticket, as she bullied her father to get his staff to look for one. Plus she was the only one who was not hounded by the press or other people.
After the success of this film, the studio had planned to adapt the sequel, Charlie and the Great Glass Elevator. However, Roald Dahl so disliked this film that he refused to sell the rights to his subsequent book. There was talk of writing a screenplay for an original sequel, but this was abandoned and no sequel was ever made.
Even though the film was made in Germanic Europe, which is world-renowned for its candies, on the DVD Commentary, Peter Ostrum said that the sweets were shipped from the United States. In his words: "They were quite stale by the time we got to them."
The transportation in the factory gets progressively smaller as more and more children are eliminated. This confirms that Wonka purposely allowed four of the five children to get hurt so he could have only one remaining child with him to make his heir.
The same year as the film's release, Aubrey Woods (Bill the sweet shop owner) appeared as The Controller in the Doctor Who (1963) serial "Day of the Daleks". Jon Pertwee, who was The Doctor in the show at the time, had been offered the role of Willy Wonka, but turned the role down, due to his commitment to the series.
When filming the scary tunnel scene, the actor's reactions in the film was genuine and they weren't acting when Wonka starts singing and has his screaming rant which was unscripted and the cast especially Peter Ostrum and Jack Albertston were terrified and had thought Gene Wilder had gone into a psychotic meltdown.
Charlie is the only child who brought a relative of the same gender (the other boys brought their mothers, while the girls brought their fathers), and the only one who brought a grandparent instead of a parent.
In the first classroom scene, the students and teacher all have the same textbook on their desks. That textbook was: "Biological Science: Patterns and Processes", published by Holt, Rinehart & Winston, 1966 and 1970.
If you look closely during the "Candyman" musical sequence, Bill the candy shop owner accidentally hits a girl in the face when he opens up the counter. This may had been purely accidental and unscripted but this has let to speculation by fans of the movie that the character is not a nice character because he willingly throws candy at the rich kids whom come into the store and when Charlie comes into the shop for candy, Bill gives him that "you better pay me" look and lectures Charlie about eating too fast and he doesn't demands payment from the rich kids.
When Mel Stuart took the book to his producer friend David L. Wolper, he didn't know that Wolper had been in talks with the Quaker Oats company about finding a film property that could accommodate some product placement for them. This led to the creation of the Wonka Bar, a major innovative collaboration between sweet manufacturer and film company at the time.
The scary tunnel sequence was written to teach children an very important lesson that the world and even your life most of the time is not in your control and that things can get confusing and messed up really fast and that you can panic and get stressed really fast, or you can enjoy the ride.
When Mr. Turkentine, Charlie's teacher, asks Charlie out of one thousand Wonka bars, how many did he open, and Charlie said, "only two". Mr. Turkentine tells Charlie he can't figure out the percentage of two out of one thousand Wonka bars. Two out of one thousand is 0.2 percent.
The film uses various footage from other unknown theatrical films for the boat scene as tunnel images, including a spider, a giant centipede crawling on a man's face, a human eyeball, a chicken's head cut off by an ax, a chameleon eating a bug, and Wonka's rival Mr. Slugworth.
Although Roald Dahl is credited as the film's official screenwriter, David Seltzer was brought in to do uncredited rewrites against Dahl's wishes. Seltzer's major contribution to the film was to add in the musical numbers. This was enough for Dahl to disown the film.
On Minty Comedic Art's YouTube video about the film, he incorrectly stated the character Slugworth wasn't a character in the book and had been created for the movie. Although the character doesn't appear in the book, he gets mentioned.
There were some suggestions at the time of release that the title change from "Charlie and the Chocolate Factory" to Willy Wonka & the Chocolate Factory (1971) was at the instigation of Afro-American groups to objected to the juxtaposition of the words "Charlie" and "chocolate" in the title. Racial concerns also dictated a change in the look of the Oompa-Loompas. (In the illustrations in Roald Dahl's book, they are clearly of African descent.)
The trivia items below may give away important plot points.
While rehearsing the scene in which Willy Wonka yells at Grandpa Joe and Charlie for stealing fizzy lifting drinks, Gene Wilder would hold back, and act more disappointed than angry. He did this so that, when he screamed at them during filming, the reactions of shock from Jack Albertson and Peter Ostrum would be genuine.
Contrary to popular belief both the Slugworth subplot and the Fizzy Lifting Drinks appear briefly in the novel and were not original concepts. Slugworth was indeed one of the many rival chocolate factory owners who sent many spies to steal the recipes. Wonka was forced to fire his human workers and shut down the factory for many years until he found the Oompa Loompas. This element was padded out to give another test for the morality of the children in addition to their attitude. The Fizzy Lifting Drinks are depicted precisely as they are in the book although Charlie never tasted them. The sequence with Charlie breaking the rules was added in order to lead to a more dramatic resolution in Wonka's office at the end .