"Bottles Revenge is a side-game in Banjo-Tooie in which a second player can control an enemy from the single-player game using the character of Devil Bottles. Originally believed to have been removed before release, it was uncovered by Ice Mario and SubDrag in September 2004. It begins with a cutscene showing Angel Bottles turning into Devil Bottles and explaining the premise of the side-game. Player 2 can control any enemy near Devil Bottles (such enemies are marked by purple "sparklies"). "
From the
RWP Wiki.