In the office, after Charlie is introduced to Mr. Wilkinson, Wonka puts his hands on Charlie's shoulders. You can hear Wonka say, "You've won," but his lips don't move (at 01:35:20, but it's Wonka's chin that doesn't move since the camera cut to a shot of Charlie from behind Wonka at 01:35:18 while Wonka was saying "I had to test you Charlie" and we saw Wonka's chin moving then, just before he says "You won!" without his chin moving).
When Charlie and his family are watching the television (at around 12 mins), you can see and hear the anchor talking about the chocolate bars. In the next scene when you see Charlie talking to his grandpa, you can only hear the anchor talking because in the background (Full-screen only) the television is off. Although, in the next shot the television is on again.
When the kids in the candy store are yelling, "Me, me!" their lips don't move (at 04:15 in a quick shot down on the kids with their hands up in the air when Bill, the candy store clerk is on the ladder ready to shower a hand full of candy down on them).
When Charlie presses the button in the Wonkavator, you can hear Willy Wonka say 'There it goes' (at around 1h 35 mins), yet, his mouth does not match and you can tell that his audio was edited to say that (but the synchronization seems fine in the wide screen version).
When Mr. Salt pleads with Veruca, he says four Golden Tickets remain to be found. However, he mouths "three" and holds up three fingers (at around 11 mins). The obvious audio dub indicates either an error, or that the filmmakers may have switched around the order in which the children are introduced during editing.
During the last Oompa Loompa musical number (following Mike Teevee's undoing), the Oompa Loompa in the foreground apparently doesn't know the words to the song. Similar errors occur throughout the Oompa Loompa scenes, as many of the actors spoke little or no English, and had trouble learning the songs for this reason.
Willy Wonka misquotes John Masefield's line in "Sea Fever" when (at around 1h 01 mins) he says "...and all I ask is a tall ship and a star to sail her by". The correct line is "...and all I ask is a tall ship and a star to steer her by".
In Wonka's office, the clock's pendulum (at around 1h 30 mins) should be anchored under the number six; it is off-center to the right. The light bulb in the half lamp on the desk is whole (at around 1h 30 mins). These break the harmony of everything being cut in half. While the off-center pendulum IS an error, however, the light bulb not being cut in half technically isn't. Director Mel Stuart explained that they tried to cut the light bulb in half, but doing so caused it to be unable to function. Thus they had no choice but to leave it whole.
During her TV interview, Violet says she laid off gum and switched to chocolate bars for the contest. She then proceeds to gloat about the piece of gum she's been chewing for three months, thus breaking a world record. If she laid off of gum for the duration of the contest, how is it she's been chewing this piece of gum for three months?
When Violet turns into the blueberry you can see the reflection of the blue light in her hair. But in the same scenes where blue make-up is used instead of the light, you can see the regular flesh-tone under her hair and in her parting.
When Willy is coming out of the factory, there is a large shadow crossing the walkway when the camera angle is at Willy's back. Right as he walks into the shadow (at around 44 mins), they change cameras to show him from a closer shot, and he is further back on the walkway and for the second time walks into the shadow (at around 44 mins). The actors discuss this on the 30th anniversary commentary.
When Charlie opens his first Wonka bar and says he found the ticket (at 15:19 in the wide screen version, where the bar is cropped off the bottom of the screen so we can't see it), the bar is inside the plastic casing still, but when he turns around, it is out of the casing and in his other hand.
When the Wonkavator appears for the first time (at around 1h 35 mins), it appears completely different from the one that goes through the glass ceiling (at 01:36:57, e.g., the spire is missing from its roof, and there is less exterior trim).
In the inventing room by the everlasting gobstopper machine, Veruca looks over her left shoulder at her dad(at around 1h 09 mins), and Mr. Salt is right behind her. The next shot, Mr. Salt takes a last step towards the group (at 01:09:29 where he is behind Violet), and is clearly much further to the left of Veruca. When the group is shown from the front again (at around 1h 09 mins), Mr. Salt is back right behind Veruca.
When everyone first notices the chocolate river, thinking it's dirty water, Willy says, "It's chocolate." As he is saying this, Veruca can be seen putting a piece of candy in her mouth (at around 20 mins). The camera then cuts to a close shot (at around 21 mins) of Veruca saying, "That's chocolate!?" at which point her mouth is empty and her hand is completely away from her mouth.
You can clearly see that Willy Wonka is about to turn right down the red carpet (at around 32 mins) when the shot cuts to the crowd (at 44:33 to 44:38), but in the next shot (at around 39 mins), he has been pushed back toward the end of the stairs (and doesn't reach the right turn until 44:49).
In the golden egg room there's a low piece of clear plastic on the front of the egg judging device when Veruca is standing on it (at around 1h 22 mins). When Mr. Salt chases after Veruca down the same chute (with pegs on the gold pole to the left at 01:23:00), the piece of plastic is gone.
In the golden goose room the hallway leads directly into the room via an archway with no door (at around 1h 19 mins). Later (at around 1h 22 mins) when Veruca is singing, the archway casts a shadow on a wall inside of it that completely blocks off the entrance. After the song has concluded the entrance is opened again (at around 1h 22 mins).
At the start of the movie when all the children are in the sweet shop, Bill the shopkeeper lifts up a section of counter to go to the customer side of the counter (at around 52 mins) and does not put the section of counter back down. Bill returns to behind the counter through another section of counter (at around 5 mins), and then re-opens the first section of counter to let the kids behind the counter (at around 50 mins). Also, when he lifts up the counter the second time, a girl by the counter with a white ribbon in her hair clearly gets smacked on the chin by the rising counter.
Before Mike Teevee gets taken away, the Oompa Loompa shoe pom-poms (pompoms to the purists) are white (at around 1h 30 mins). When the Oompa Loompas start singing (at around 1h 30 mins) the pompoms are suddenly orange. When the Oompa Loompas first appear at 56:58 (and sing their first chorus at 01:00:10), their pompoms are white with brown stripes to match their outfits which they also wear in the Inventing Room where they sing their second chorus at 01:13:12, the golden egg room where they sing their third chorus at 01:23:23, and the Wonkamobile room. The Wonkavision room, where Mike Teevee gets transmitted, appears as a clean room where the Oompa Loompas wear white outfits with no piping. They sing the last (fourth) chorus at 01:30:28 in the clean room wearing white outfits with orange piping and pompoms that match the Oompa Loompas' faces.
Mrs. Teevee starts out with a black purse, which she then carries throughout the movie (from 42:28 before Willy Wonka appears to 01:26:29 just before donning a clean suit). Once she is in the TV room, however, she has a white purse (it can be noticed at 01:27:15 when the giant Wonka Bar is carried in, and also when Mike gets shrunk and Mrs. Teevee sticks him into the purse).
The two doors that Willy Wonka exits while coming out of the factory are fully lit (at 43:54, 44:03 and 44:17), but in the next shot (at 43:52, 43:58, 44:15, 44:26), from the point of view of the crowd, the right door is shadowed.
During the overhead shot of the guests watching the Wonkatania boat approach them, Violet is seen tossing her giant Gummi Bear to the ground, however in the next shot from behind the guests and the subsequent front shot as they walk over to the boat and Charlie says "Wow! What a boat!" Violet is seen holding the Gummi Bear under her arm again. It disappears permanently when she boards the boat.
When Mike Teevee gets thrown back into the pots/pans after eating the exploding candy in the inventing room, you can clearly see the line attached to his belt that was used by a crew member to yank him backwards (at 01:07:53 as the rack is falling backwards).
In the fizzy lifting scene (01:16:12 to 01:18:59) you can clearly see the rigging for the actors (for example, two cables holding up Charlie by his waist at 01:16:17 when he is holding onto Grandpa Joe as they are horizontal along the bottom of the superstructure). And if you look closely you can even see the hooks they're attached to (for example, on Charlie's left side of his waist when he somersaults at 01:17:18).
Although the film is set in a mythical English-speaking country, German license plates can be seen (at around 24 mins) as Charlie walks past a restaurant while his mother is singing "Cheer Up, Charlie".
The liquid issuing from the beehive on the machine that makes the chewing-gum meal (at around 1h 11 mins) is probably not honey, as cold or room-temperature honey is more viscous. Hot honey can drip at that speed.
When everyone is in the hallway outside the nerve center (at around 1 min), they are all crouched down; when Wonka opens the door (to the Chocolate Room) they are all standing up straight with 6 feet of room on top of them (at around 4 mins). The room and hallway are full of other such optical illusions, so this is clearly an intentional artistic effect.
When everyone first enters the Chocolate Room containing the chocolate river (at around 1 min), the cast enters in reverse order of how they were positioned to in the previous scene when Wonka plays the musical lock on the door. This may be a continuation of the paradox hallway gag.
When Augustus is stuck in the chocolate river pipe, Willy Wonka states that the pressure of the chocolate behind him will eventually push Augustus through. When Augustus is eventually pushed up the pipe, the chocolate behind him, which should be moving at the same rate that Augustus shot up, is moving at a much slower rate.
When they are going through the tunnel of horrors, they are presumably traveling at a great speed. However there is no wind. In fact, this is due to the fact that the director and the wind-machine operator had a "blow-out" that day, and the director chose to shoot the scene without wind.
The first time you see the world map on the news (at 13:30, indicating where the gold tickets are found), there is a hole/tear in the map around Montana - this is the place where the marker "3" will be placed in later takes.
When Mr. Wonka is in the television room and walks from the platform to the camera you can plainly see the ceiling of the sound stage, because the sound stage ceiling is black in comparison to the white room. (Not on wide screen.)
In the golden egg room when you see the egg fall from the top part onto the chute the golden goose is not visible, instead you can clearly see through the hole where the set ends. (Not in the wide screen version.)
When the great glass elevator is going up and out you see numerous windows, during exterior shots none of these windows are seen at any point, in fact all the windows from the exterior of the factory don't match any of the exterior windows.
In the invention room when Willy Wonka adds the coat to the mixture that was "too cold" (at around 1h 08 mins), you can see there is no liquid in the pot, just smoke. As he stirs it you can clearly see no liquid in the pot.
While Grandpa Joe and Charlie are singing "I've Got a Golden Ticket" Grandpa Joe goes and opens a window, then shouts to anyone who might be outside, "Good morning, look at the sun!" When Grandpa Joe opens the window, it is obvious that there is no glass in the window frame.
When Willy Wonka does his somersault on his way to meet the children (at around 15 mins), the mat on which he lands is visible under the carpet. (In the wide screen version, only a shadow the low sun casts to the left of the carpet where it is raised can be seen.)
After Willy Wonka shuts off the Everlasting Gobstopper machine, he goes to pick one off the conveyor belt to show to the guests. The conveyor belt pulls up briefly with the Gobstopper (at around 1h 09 mins), revealing it was previously stuck to the belt.
While riding the Wonka-mobile you can clearly see that the pipes and computers are reused from the inventing room, in fact there's a yellow pipe labeled E3 (at around 1h 26 mins) which was previously seen in the inventing room (at around 1h 10 mins) near the great gum machine. As well as the windows and brick walls which suspiciously seem to have the same dimensions as the ones in the chocolate room.
When Wonka first allows the children into the chocolate room he makes an umbrella by sticking the bottom of his cane into a "mushroom" top and then holding the cane upside-down. As he twirls the umbrella you can see the stab holes in the Styrofoam bottom from prior takes (at around 18 mins).
When Mike Teevee is telling his mom he feels fine after he got shrunken and put into the television, you can see where his platform ends to the left (at 01:29:29 after he has jumped down from the screen, but the platform on which he is standing can't be seen on the wide screen version which crops the platform and crops his feet at mid-calf).