Spoiled Rotten is the first boss from Wario Land 4, fought after completing the first level. It resembles a giant, purple, anthropomorphic eggplant and has numerous childlike traits (such as carrying a doll).
At the beginning of the fight, Spoiled Rotten is assisted by two smaller eggplant creatures and simply walks around harmlessly, making it easy to hurt. However, after taking a certain amount of damage, Spoiled Rotten transforms into a terrifying and demonic monster with sharp fangs and grotesquely distorted features. When defeated, Spoiled Rotten explodes into a shower of smaller eggplants and can never be re-fought unless starting a new game.
- On Wario Land 4's Normal and Hard modes, Spoiled Rotten is the easiest boss in the game by ridiculously far, requiring absolutely no effort or strategy to beat (apart from figuring out how to jump over it during its final phase, at least). On the game's Super Hard mode, however, Cuckoo Condor (who is normally the game's second easiest boss) replaces Spoiled Rotten as the game's easiest boss, with Spoiled Rotten itself becoming the game's hardest boss by shockingly far due to the fact that the time limit for beating said boss is reduced from thirty seconds (in Hard Mode) to fifteen seconds, meaning that players have to beat said boss literally as fast as they possibly can in order to be able to kill it before its time limit kills Wario.
- Spoiled Rotten's room contains not one, but two cameo appearances of the Nintendo GameCube.
- Spoiled Rotten's design eerily resembles Kirby from Nintendo's Kirby franchise, especially during its first phase.
- The Eggplant Warriors that initially (attempt to) serve as Spoiled Rotten's bodyguards are basically re-skinned Totsumen, foreshadowing the recurring appearances of said enemies in the game's later levels.