Charles Schulz' wanted to call his comic strip CHARLIE BROWN, but the editors were worried about legal action from people who had that name. It started publication as L'IL FOLKS, but because that was the original title of someone else's strip, his syndicate forced the title PEANUTS on him. He hated the title (partly because it made people assume the character's name was Peanut) and didn't use it in any of the specials or movies, which were titled CHARLIE BROWN or SNOOPY.
Various steps were taken with the animation to emulate the original look and feel of the comics and the previous animated specials. For example, the trees and other foliage in the background are static and never billow or sway in the wind. Even on the characters, their animation appears "jagged" and skippy. This was done to emulate the low quality hand drawn animation that the Peanuts television specials were known for.
The name of the Little Red Haired Girl is seen on the list of student's rankings on the standardized test. She is #4 on the list and her name is indicated as "Heather Wold". The name 'Heather' was first attached to her in the special It's Your First Kiss, Charlie Brown (1977) in 1977, although Charles M. Schulz didn't consider it canonical.
When Snoopy enters his dog house to fetch the instructions in order to help Charlie Brown learn to dance, he throws a bunch of stuff out. Among those, is the painting "Starry Night", by Vincent van Gogh. This is a reference to a running gag in the comic strips, when Snoopy is mentioned to owning a Van Gogh (though the picture is never actually seen).
Kristin Chenoweth, who voices Fifi, won a Tony Award for her portrayal of Sally Brown in the 1999 Broadway revival of the musical "You're A Good Man, Charlie Brown". This is also her third animated role in a Fox movie.
The dance moves the kids have are almost 100% the same as in A Charlie Brown Christmas (1965). Except Schroeder's was an add on, for he played the piano in the Christmas special instead of dancing. Also Violet and Patty did opposite dance styles, in accordance from the Christmas special.
While the World War I Flying Ace is struggling to return to his airfield, he is briefly shown sporting a wiry mustache as he is crawling through the desert. This is a reference to Snoopy's brother Spike, who was named after Charles Schulz' childhood dog and appeared infrequently in the comics. Spike wore the same mustache and lived in the desert country near Needles, California.
The Beagle Scouts, Snoopy's bird friends who all resemble Woodstock, appear in the film as the pit crew for Snoopy's plane in the World War I Flying Ace sequences. The birds are named Conrad, Bill, Olivier and Harriet. In the comics, Harriet is generally portrayed as the toughest while Olivier (likely the bird who appears to mess up constantly in the movie) is the dumbest.
On the list of posted standardized test grades, the name "Heather Wold" is seen. "Heather" was the name given to the little red-haired girl in "It's Your First Kiss, Charlie Brown (1977)." Donna Wold was Charles Schulz's red-haired girlfriend, who turned down his marriage proposal in 1950 (the same year the comic strip began) and upon whom the unattainable character in "Peanuts" was based.
Charlie Brown hands Patty and Violet a comic book with Spark Plug the Horse from the comic strip "Barney Google" on the cover. Peanuts creator Charles M. Schulz's nickname was "Sparky" after this character.
Snoopy's siblings, Andy, Olaf, Marbles, Spike, and Belle, appear in the mid-credits scene. Two additional siblings, Molly and Rover, were created for the televised specials but not by Charles M. Schulz himself and are omitted from the scene.
On the back of the "Spark Plug" comic book Charlie Brown recommends to Patty and Violet, a LI'L FOLKS panel can be briefly seen with Patty and Shermy. "Li'l Folks" was a single-panel comic strip drawn by Charles M. Schulz from 1947 to 1950, and a precursor to the "Peanuts" strip.
There is a series of numbers on the test rank list for Charlie Brown's class, 555 95472, which is actually the name of one of Charlie Brown's classmates. 5 (as he calls himself) first appeared in the Peanuts comic strip from September 30-October 4, 1963. He has two little sisters, 3 and 4.
The Royal Guardsmen sang "Snoopy vs. the Red Baron", "The Return of the Red Baron", and "Snoopy's Christmas". These three songs are a trilogy. "Snoopy vs. the Red Baron" is one of the greatest novelty songs ever released during the 1960s. It was #2 on the US Billboard Charts during the last days of 1966. Other Snoopy songs by the Royal Guardsmen are "Snoopy for President" (1968) and "The Littlest Astronaut" (1978)
Until this movie came out, no Peanuts character was ever shown from any way other than the front or side. In the scene where Charlie is learning how to dance, he briefly does the Chicken Dance and turns around to wiggle his backside during that move in the dance.
At some points, the author named "Warren Piece" and the book titled "Leo's Toy Store" is mentioned. The children's book of the same name by the said author has released in bookstores on November 20th, 2015, exactly two weeks after this movie released.
Linus is in Charlie Brown's class even though he is about a year younger than the rest of his friends, because he skipped a grade. At the time the comics were written, the practice of skipping a grade was more commonplace, as there were no advanced classes or special programs for gifted children. It's important to note that throughout the strip's history, the intelligence of Linus and all of the characters has been highly exaggerated for their age for comedic purposes. This explains why the supposedly 7 and 8 year old children can discuss philosophy and literature at an adult level.
The filmmakers deliberately emulated the style of the original Peanuts television specials, which explains why many of the elements appear static or inconsistent. For example, the snow falls straight down apparently without being affected by the wind, because it had that static consistency in the animated specials.
In the pre-release promotion of the film, there were specific reassurances to the property's fans that its score would include compositions of the musician most famous for his music for the property, Vince Guaraldi, where appropriate. Indeed, the music can be heard in numerous sections such as the opening skating pond scene that includes "Skating" and "Linus and Lucy."
To simplify the characters for the film, some subtle adaptational changes were done. For instance, the kids of Charlie Brown's neighborhood are in different grades and classes in their school while Peppermint Patty, Marcie, and Franklin are in another school altogether in the comic strip. For the film, all the kids are in the same class in the same school.
The trivia items below may give away important plot points.
After Charlie Brown becomes popular, the kids struggle over who gets his attention. Shermy (who has not appeared in the film to this point) grabs his arm and says, "I saw him first!" In the very first Peanuts strip printed, Charlie Brown walks by and Shermy is indeed the first character to ever see him.
On the list of highest standardized test scores, the name "Heather Wold" can be seen as the #4 highest score. This most likely is the name of the Little Red-Haired Girl. The Little Red-Haired Girl's first name is "Heather" in the 1977 special It's Your First Kiss, Charlie Brown (1977) - it should be noted, however, that Charles M. Schulz never considered the television specials to be canon. "Wold" comes from Donna Wold, the woman who inspired the character. Wold dated Schulz for three years, later turning his request for marriage down. The two remained close friends until Schulz' death in 2000.
When Charlie Brown (erroneously) finds that he got a perfect score, Patricia Reichardt's "Peppermint Patty's" test score of "65" can be seen at the bottom at #14. This is not only Charlie Brown's real score on the test, but also alludes to the gang's 65th anniversary.
When Snoopy is trying to use the typewriter the first time, his little bird friend gets stuck in it. Snoopy then types random letters and punches a "W" on his friends forehead. This stands for "Woodstock" the yellow birds name.
The Red Baron's plane has been in the air throughout the movie since it has been used during the classroom scene, and then after the credits, the engine on the plane has broken down and it fell into a pond.
Just like in the comic strip, Linus is seen in the same class that Charlie Brown is. Considering Linus' age (being younger than Charlie Brown), this would imply that Linus is a brilliant genius; Linus even analyzes Charlie's essay on Tolstoy's "War & Peace" and notes that is really good. However, he gets to be 5th in the list of best degrees about the School's Standarized Test.