Baby Mario: Baby Mario is the first character that will join your party. He is able to make Yoshi run very fast, and is also able to hit M blocks. Yoshi's eggs will also bounce off walls.
Baby Peach: Baby peach will allow Yoshi to glide longer, and will allow him to soar in the air if there's wind.
Baby Donkey Kong: Donkey Kong is able to smash through enemies, climb on vines, and make Yoshi's eggs blow up.
Baby Wario: Wario will be able to use his magnet to move metal and coins.
Baby Bowser: Bowser is able to shoot fire balls out of his mouth. Yoshi can not eat when Baby Bowser is on his back.