An old computer game on the PC, Macintosh, and Amiga, which pitted four multicolored puffballs against numerous levels which became progressively more difficult. The blue puffball could swim, the yellow one could shoot fireballs a-la Mortal Kombat fighters, the red one could bite through particular types of bricks, and the green one had a kick-ass grappling hook. Once each fuzzball was activated by crossing through a field of its color, you could switch between them at will - animated by the fuzzy things changing into a band of swirling pixels - to solve all sorts of fun problems. Horribly addictive - almost as much as Lemmings, but with more action. And a grappling hook.
/me drools over grappling hook
Update: Interestingly enough, the designers of the game, KALiSTO, took that same clever game design and made a game for the PC and Super Nintendo (and Game Boy) starring everyone's favorite ghost-gobbling yellow circle, Pac-Man, called Pac in Time. The music, game mechanics, and even the sound effects and monsters were practically lifted straight from Fury of the Furries.