Mock Up

Mock Ups, also known as Bogus Blimps , are strange balloons in Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3 that only appear in a few levels. When a Yoshi gets too close, they inflate. If a Yoshi eats one before it pops, a 1-UP is awarded. However, if the Yoshi fails to eat the balloon, the Mock Up pops and reveals a Fly Guy who then flies away, while the Yoshi is injured.

Super Mario World 2: Yoshi's Island

 * Official Nintendo Player's Guide: Also known as Bogus Blimp, Mock Up goes boom-boom when Yoshi gets close.