Mickey Mouse: Dream Balloon
Platform: Nintendo Entertainment System
Region: Prototype (USA)
Media: Cartridge
Controller: NES Gamepad
Genre: Platformer 
Gametype: Prototype
Release Year: Unreleased
Developer: Kemco
Publisher: Kemco
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Mickey Mouse Dream Balloon is a localization of the Kemco title Mickey Mouse 3: Yume Fuusen. Technically, one could argue that MMDB isn't actually unreleased, as the game was published in the US as Kid Klown, albeit with a full graphical overhaul and totally different story. The game is a simple platformer, one of many available on the NES at the time. While it isn't a bad game by any means, neither is it an especially original offering to the genre. 

This prototype is of an earlier build than the version that would become Mickey Mouse 3/Kid Klown. The difficulty was tweaked heavily between this version and the final. Enemies have different patterns, bosses take different amounts of damage, and some areas, like part of stage 2, use completely different layouts. 

http://forums.lostlevels.org/viewtopic.php?t=1391