Bonecoaster is an ally only appearing in World 8-7 in New Super Mario Bros. Wii. They prevent them from falling in the lava in the air. Bonecoasters don't hurt anyone. If all of the players Ground Pound at the same time, then Bonecoaster will fall into the lava.
Attention MarioWiki users!: This article is too small or lacks sufficient information. Whether you are commenting or editing, we would be pleased if you help MarioWiki by expanding it.