Poison Mash is a terrible fungus-like creature found in Revenge of the King in Kirby Super Star Ultra as a replacement for Cappy. Where Cappy was replaced by the delectable dessert-like creature, Blopper, in the extra game in Kirby's Dream Land, this toxic mushroom-like creature takes over his role in Super Star Ultra. Poison Mash behaves the same way Cappy does, as he wears his little mushroom cap and slowly hops his way to Kirby. Like Cappy, he occasionally tosses his cap towards the air. If Kirby destroys the cap, Poison Mash has no choice but to flail his way into Kirby. Like Blopper, Poison Mash has far more health than Cappy.
Poison Mash appears as a withered, corrupted Cappy. Thus its color pallate and appearance contrast with Cappies. Its mushroom cap is flatter than a Cappy's, and is dull blue with bright pinkish-purple spots splattered over it. It always has a meloncholy frown and its body is pale gray in color.