Bone Piranha Plant

The Bone Piranha Plant is a subspecies of Piranha Plant debuting in New Super Mario Bros. 2. They are skeletal versions of their relatives with some changes, such as: a grayish cranium, holes rather than spots, greenish-gray lips, vertebrae instead of a plant stalk and grey, dark grey leaves that appear dead.

New Super Mario Bros. 2
Besides these graphic changes, its attack patterns appear the same than those of a regular Piranha Plant. However, unlike normal Piranha Plants, they are immune to fireballs. They can be defeated by a Super Leaf tail spin, Super Leaf, Star or a Gold Flower, however. They are only found in Fortresses and Castles.

Mario Party: Island Tour
Bone Piranha Plants also appear in Mario Party: Island Tour on the Bowser's Peculiar Peak board. If the player lands on a space that moves them forward a number of spaces, the Bone Piranha Plant appears, chews them up, and then throws them forward.

Mario Kart 8
In Mario Kart 8, Bone Piranha Plants are set to appear as obstacles in the course, Bone Dry Ruins. It is currently unknown if they will act as normal Piranha Plants in the Mario Kart games and attack the driver.