Speed-Eater

From the Super Mario Wiki

Speed Eater is an unlockable minigame in Yoshi's Island DS. The player controls a Yoshi in a long room full of enemies and must try to make as many eggs as they can by eating enemies. A Hard Mode can be unlocked by collecting all eight Baby Coins in World 4.

[edit] Easy Mode

Players have 30 seconds to eat and make eggs out of Shy Guys and a few harder enemies.

[edit] Hard Mode

This mode has many more difficult enemies, some of which can't be eaten, however you are given 60 seconds to beat this challenge.