Shelly

Shelly is a particular egg that contains Birdo in Super Mario RPG: Legend of the Seven Stars. It has pink spots on it, similarly to a pink Yoshi egg. It is the first Birdo egg in the series to be depicted this way.

Mario and his allies discover it in Nimbus Castle, under the care of a Shy Away while the castle has been taken over by Valentina. Birdo speaks to Mario from inside the egg, asking him to play with her. Accepting her request will start her boss fight.

Shelly serves as the first phase of the battle against Birdo. In battle, it has a different appearance, featuring smaller red splotches in place of its pink spots. Shelly poses no threat whatsoever, and must simply be attacked to deplete its HP and destroy it. When this occurs, Birdo will hatch, beginning the real fight.

Despite being destroyed over the course of the boss fight, Birdo will be inside Shelly once again after the battle.