Mecha Piranha Plant

Mecha Piranha Plants or Piranha Plant (mechanical) are course hazards that appear in Waluigi Stadium in Mario Kart: Double Dash!!. Paired with Podoboo Cogs, they are found on the long straight of the course pointing south. They slowly come out of mechanical green Warp Pipes; they serve as a wall and cause players to stop when they are bumped into and they cannot be destroyed. A total of three appear in the course. They reappear when Waluigi Stadium returns as a retro course in Mario Kart Wii.

Mario Kart Wii official game guide bio

 * "Sliding horizontally out of a giant green pipe, these are part of the scenery. Dodging is the only way to avoid them."