Mock Up

Mock Ups, also known as Bogus Blimps, are balloons in Super Mario World 2: Yoshi's Island and its remake, Yoshi's Island: Super Mario Advance 3, that appear in only a few levels. When a Yoshi gets too close to Mock Ups, they inflate. If the Yoshi eats one before it pops, a 1-UP is awarded. Failing to eat the balloon results in it exploding and revealing 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.