Yellow Shell (Super Mario World)

The Yellow Shell is an unique item in Super Mario World.

Appearance
The Yellow Shell has a yellow back and a hole for a koopa to fit in on the bottom.

Trivia

 * The Yellow Shell isn't something Mario/Luigi can absorb.
 * If Yoshi swallows the Yellow Shell then two clouds surround him and any nearby enemies flip over and get defeated.
 * This item is surprisingly common.