The music that plays when Yen Sid is seen painting is the Sorcerer's Apprentice Theme from Fantasia, the 1940 Disney animated movie where he made his first appearance.
The Mickey Junk Mountain area is based off of the Matterhorn attraction from Disneyland. But Instead of snow, its made out of actual Mickey Mouse merchandise produced throughout the years.
In Mickey Junk Mountain, a can with Donald Duck holding a glass of juice is seen among the piles of junk in the game. This is a reference to a brand of orange juice from the Florida's Natural Growers agricultural cooperative that used Donald Duck to market its orange juice, even using Donald as its mascot.
During development, the bunny children came in four different colors: black, white, light red, and light blue. The final game features only light blue bunnies.
In the E3 trailer of Epic Mickey, the Mad Doctor is seen in the black cape uniform like in the cartoon 'The Mad Doctor'. This was changed in the final game to avoid confusing him with the shadow blot.
When first meeting Gremlin Calvin in Dark Beauty Castle, he is wearing a yellow suit. When saved, he reappears in Gremlin Village, now sporting a green suit.
It was originally intended for Wonderland to appear in the game. The world can still be seen in the opening and closing cinematics.
Mickey is aided throughout the game by Gus and other creatures based off of "The Gremlins", an unproduced film collaboration between Disney and author Roald Dahl that dates back to World War II.
According to Warren Spector, there were originally three different designs for Mickey, with his appearance changing based on whether the player made heroic or mischievous choices. The designs were based off different eras of Mickey Mouse cartoons. Hero Mickey was based on his old movie posters, Wasterlander was based on 1930s vintage Mickey, and Scrapper was inspired by the early black and white Mickey cartoons (along with the 1995 Mickey Mouse short 'Runaway Brain').
Mickey was originally to have released his own paint from his hands. As he did this, the paint from his body would vanish, revealing his outline. The idea was later scrapped, and Mickey was given a paintbrush instead.
In an early version Gus was to be caged like all the other Gremlins in the game as opposed to being free by default. This may explain why Gus never introduces himself to Mickey, as the scene where he would have done so was cut and never replaced.
Originally, if Mickey used too much thinner when he was in his 'scrapper' mood, he would've turned into a design called 'Thinner Mickey'. Every evil action that Mickey would have done erased his paint and showed more of his basic line-art. The idea was eventually scrapped due to the Disney company not wishing to tarnish Mickey's 'heroic' attitude.
In the original script, Oswald was going to be the main antagonist, but was replaced with the Blot in order to avoid hurting his reputation by portraying him as an unlikable character.
During the ending, Spoiler:the Gremlins use a recolored model of Gus. Due to this, every Gremlin has Gus' hat and mustache.
Minnie Mouse was originally going to appear in the ending, where Oswald was to sneak in and interrupt her kiss to Mickey.
While Disney produced a number of Oswald cartoons, Universal distributed them and owned the rights to the character. In order to acquire the rights to use Oswald, Disney made a deal that included trading the services of sportscaster Al Michaels to Universal to get Oswald the Rabbit back.
In Tortooga, if the player helps Beluga Billy, he will give the player a sketch of a stop watch and say "It's dangerous to go alone! Take this." This is a reference to the original The Legend of Zelda.
Oswald's original love interest, Fanny, was set to appear in the game. She was dropped in favor of Oswald's last love interest, Ortensia.
When Mickey meets Oswald for the first time, Oswald is cleaning a little bunny doll of himself that is kept in a glass case. The doll itself is based on the very first product of Oswald the lucky rabbit, and was made when Walt Disney still owned the character. The doll itself is considered a collectible.
Originally Mickey's design would change based on how you played the game. Hero being good, Wastelander being anti-hero and Scrapper being bad. Due to negative feedback of Scrapper mickey's personality the three designs were scrapped.
Many areas in the game are taken directly from areas of Disney Land and scenes in Disney animations.
The Lonesome Manor is not based on any one Haunted Mansion Ride but all of them. Plus, there are three cameos from past Disney character. A painting of Chernabog (the demon from Night of Bald Mountain from the movie Fantasia), Madam Leona (the head in the Crystal Ball), and The Lonesome Ghosts (from Mickey Mouse Cartoons).
The gameplay design was inspired from the action of the old school Legend of Zelda games, the platforming of Mario and the RPG elements of Deus Ex.
On Mickey Junk Mountain (Wasteland version of the Matterhorn) you can see a number of old NES and SNES Mickey Mouse game cartridges made by Capcom.
There is a hidden room on Mickeyjunk Mountain containing a basketball backboard. It is a tribute to a secret half court in the peak of the Matterhorn Bobsleds ride at Disneyland which employees built for use between shifts.