Baby Yoshi

Baby Yoshi is the younger form of Yoshi, first seen in Super Mario World, and later seen in the Yoshi puzzle game and Yoshi's Island DS.

Super Mario World
In Super Mario World, red, yellow, green and blue Baby Yoshis are found in Star World, where they hatch from eggs of the same color whenever the player makes his approach. Feeding the Baby Yoshis roughly five enemies will make them turn into adult Yoshis; however, if a Baby Yoshi eats any powerup, it'll grow up instantly. Also, all the eggs Mario rescues from the Koopalings hatch into Baby Yoshis during the ending cutscene. Yoshi himself hatches directly into an adult when the player uncovers his egg, but this is because Bowser trapped Yoshi in the egg.

Yoshi
Baby Yoshis are seen in the title screen.

Yoshi's Island DS
A Baby Yoshi was born in the end of Yoshi's Island DS that is one of the Star Children. He is possibly the baby form of Yoshi.