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; if they are under the Super Star's effects, however, 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 the Poison Mushroom, Zombie Shroom, and Ghoul Shroom.

Interestingly, the Story Mode level Begone, Rotten Mushroom! implies that Rotten Mushrooms are regular Mushrooms that rotted over time and became vengeful.