The Ramblin' Evil Mushroom originated from Earthbound. It was an enemy that would spread its spores on Ness, which would cause a mushroom to grow on Ness' head. While Ness was affected by the spores, your control inputs would switch around at random, making it very difficult to navigate Ness' surroundings.
The Ramblin' Evil Mushroom is a shooting item that works like the Fire Flower. Once picked up, the user can shoot spores from the mushroom. The spores grow a mushroom on the opponent's head, when large enough, like in the Earthbound, it reverses the left and right inputs. This can backfire.