Tramplin Stus are beta enemies that was originally planned to appear in Super Mario Sunshine.
Appearance
They were featured in the Spaceworld trailer, but never made it into the final release. However, its files still exist in the final game.
Battle
Their only attack was to run into the player or simply drop a Swoopin' Stu or a Strollin' Stu. However, no goop was found near a Tramplin Stu for a Swooping Stu to occur.