Baby Bowser's pet
From the Super Mario Wiki, the Mario encyclopedia
Baby Bowser's pet is a large, green, snake-like ghost that Baby Bowser rides in Yoshi's Story. These strange apparitions have the ability to fly. They appear in the final boss fight of the game. Baby Bowser gets on them, so if a Yoshi tries to throw an egg at Baby Bowser, the egg hits these pets. They are invincible, as the eggs merely bounce off the pets. Instead, Yoshi has to either throw eggs at the ceiling (which is littered with spikes) to make the spikes fall down and land on Baby Bowser or explode the eggs in front of Baby Bowser's face.
Names in other languages