Mock Up

Mock Ups, also known as Bogus Blimps, are balloons in Super Mario World 2: Yoshi's Island and its reissue, 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 that 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.

Yoshi's Island: Super Mario Advance 3

 * Shogakukan guide: しばらくすると破裂して消えてしまうが、その前に食べれば１UPゲット. タマゴをぶつけると転がっていってしまうので注意. (It will burst and disappear after a while, but if you eat it before that, you will get 1UP. If you hit it with an egg, it will roll away, so be careful.)