Biting Bullet Bill
From the Super Mario Wiki
Biting Bullet Bills are unused enemies in the SNES game Super Mario World 2: Yoshi's Island. These Bullet Bills and their Bill Blasters are dark red, and much like Missile Bills, they chase after Yoshi. As they move through the air, their mouth makes a two-frame chomping motion. If it hangs around for too long, it will disappear in a pop. They can be defeated by simply stomping or swallowing them; it looks like a regular Bullet Bill if spat back out, but it will fly downwards. In the Game Boy Advance port, Yoshi's Island: Super Mario Advance 3, they are used and make their only appearance in the level Endless World of Yoshis.