Rotten Mushroom

Rotten Mushrooms are purple, skull shaped mushrooms that appear in Super Mario Maker 2. They replace 1-Up Mushrooms when the night mode is activated, but only for the Ground course theme. Unlike most mushrooms, Rotten Mushrooms actively pursue the player, even jumping up ledges up to two blocks high to get to them. However, if they are under the Super Star's effects, Rotten Mushrooms will evade them. Touching a Rotten Mushroom powers down the player, similar to a Poison Mushroom, making it a hazardous obstacle. Their skull-like design and role as an "evil" counterpart to "good" mushrooms makes them comparable to Poison Mushrooms, Zombie Shrooms, and Ghoul Shrooms. The Super Mario World version of the Rotten Mushroom resembles Bowser's fireball rain from said game.

Two Story Mode levels posted by World-Renowned Chef imply that Rotten Mushrooms are Super Mushrooms that have rotted over time and became vengeful.