Proto:Mickey Mania: The Timeless Adventures of Mickey Mouse (Genesis)

General Differences

 * The game boots up with a basic SEGA screen instead of the one from the final, then cuts straight to the menu without any title screen or anything.
 * All of the menu screens use the same Mickey head background.
 * The menu cursor is an extra life item instead of a pencil.
 * There is music in the options screen that is cut from the final.
 * There is no easy difficulty setting.
 * Lives settings include two, three, and four instead of three, four, and five.
 * Help screens aren't programmed in yet.
 * "Table" song is a duplicate of "Garden" in the sound test.
 * "Dungeon" song in the sound test is "EOL Boss 3" from the final.
 * "EOL Boss 2" (the gurney ride music in the final) is absent.
 * Sound effects are labeled differently in the sound test.
 * The "Think..." voice sample is labeled as "Hmmm..." in the sound test.
 * Pluto does not make barking sounds.
 * Some animations repeat voice samples constantly (e.g., when Mickey lands after falling from a high place).
 * No death animations.
 * The continue screen has a completely grey background and the text reads "Press a key to help Mickey continue in his quest." instead of "Press a button to help Mickey continue his adventure."

Steamboat Willie

 * Voice samples used when Mickey interacts with the "Steamboat Willie" Mickey are different. In the prototype "Hiya pal!", "Wow!" and "Watch out!" are used, while the final uses "Hmmm..." and "Uh-oh!"
 * Parrots don't squawk when you attack them.
 * When Mickey defeats the cranes, the cranes don't stop completely and instead move off the screen, and Mickey does not run into the "Steamboat Willie" Mickey.
 * The message screen at the end of the wharf level says "Mickey has stopped the cranes from causing any more trouble!" instead of "Mickey has stopped the cranes and rescued Steamboat Willie!"

The Mad Doctor

 * Mickey yells "Watch out!" instead of "Uh-oh!" when a skeleton drops down.
 * The gurney ride level uses the normal boss theme.
 * The tower descent level has no sound effects.
 * When Mickey meets the "Mad Doctor" Mickey he says "Uh-oh!" instead of "Hiya pal!".
 * The message screen that appears after the "Mad Doctor" Mickey encounter begins with "Whoops!" instead of "Yikes!"
 * The chemical dispensers in the last level have different graphics.
 * When Mickey rescues Pluto, he says "Here boy!" instead of "C'mon Pluto!".

Moose Hunters

 * The first level plays the Steamboat music instead of the dungeon theme from the final.
 * Mickey says "C'mon Pluto!" at random points in the first level.
 * Mickey says "Watch out!" instead of "Uh-oh!" when a moose comes in from the left of the screen.
 * Pausing and unpausing during the first level will cause the game to lock up due to the DMA exceeding the frame limit and display an error handler titled "WELCOME TO BUG WORLD" that features a scrolling "AND MORE BUGS AND YET MORE BUGS" background. The font used here is from Puggsy.
 * The "Moose Hunter" Mickey doesn't appear at the end of the first level.
 * The "Mickey has found Moose Hunter Mickey, but has also found a moose!" message before the moose chase level is not there.
 * The moose chase ends a little bit earlier.

The Lonesome Ghosts

 * Mickey says "C'mon Pluto!" at the start of the basement level.
 * Mickey says "Here boy!" at the start of the corridors level.
 * "Lonesome Ghost" Mickey does not appear at the end.
 * The message screen at the end of the corridors level says "Whew, that was close! Mickey has escaped from the lonesome ghosts!" instead of "Phew, that was close! Lonesome Ghost Mickey has been rescued and Mickey has escaped!"

Mickey and the Beanstalk

 * The cartoon's title in this prototype is "Fun and Fancy Free", a 1947 film that originally debuted "Mickey and the Beanstalk".
 * Garden music plays on the table level.
 * The table level ends a little early, with no "Beanstalk" Mickey present.
 * The message screen at the end of the table level says "Mickey has escaped to freedom from the giants castle!" instead of "Mickey has managed to find Mickey and the Beanstalk Mickey!".

The Band Concert (Bonus Level)

 * The message screen that appears when Mickey enters this level begins with "Outstanding!" instead of "Wild!"
 * The message screen that appears when Mickey falls out of the level begins with "Unlucky!" instead of "Oops!"
 * The reward for completing this level is three extra lives. In the final, the reward is an extra continue.

The Prince and the Pauper

 * The dungeon level plays the "EOL Boss 3" music.
 * Pauper Mickey does not appear at the end of the library level, and the "Mickey has found Pauper Mickey" message does not appear.
 * Prince Mickey is missing at the end of the dungeon. Instead there's a key, and getting it will finish the level.
 * The message screen after the dungeon level says "Mickey has found the key to the tower, but now has to find Pete!" instead of "Mickey has found the prince who shows him the way to Pete's tower."
 * The tower ascent level plays the normal boss theme and has no sound effects.
 * The auto-scroll section full of weasels inside Pete's tower plays the normal boss theme, and the level itself is glitched as the fire rises faster than the screen scrolls, therefore Mickey will always die when he reaches the end of the section, therefore making the level impossible to complete.
 * The message screen before the final battle says "Mickey must now face the might of Pete in the final showdown!" instead of "Mickey must face the biggest Pete of all in the final showdown!". This was found via hex editor.