Relay Heihō

Relay Heihō are bomb-dropping Boo Guys from Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, and Yoshi's New Island.

Super Mario World 2: Yoshi's Island
They are found stationed in long rows within the ceilings of certain castles. They relay a single purple bomb, dropping it when a Yoshi approaches them. The Yoshi can perform a Ground Pound to force them to drop the bomb. If they miss, the one who dropped it will hang its head with an ashamed expression, with them starting over a few moments later. Due to their position, they cannot be defeated.

Yoshi's New Island
They reappear in this game, with the same function as before. However, in Yoshi's New Island, they no longer change expression when the player has ground-pounded, however, there are still texturing for that, so this may be unintentional.