Rex

A Rex is an enemy that first appeared in Super Mario World. It is a purple dragon with wings but can't fly.

Super Mario World
In Super Mario World, it was one of the first enemies encountered. It takes two stomps to defeat it. The first will squash it to half its height and the second will defeat it.

Mario & Luigi: Superstar Saga
In Mario & Luigi: Superstar Saga, they are found on Hoohoo Mountain with Beanies and Dry Bones. A Jump will decrease its height, and a second will decrease it even more, making it easier to dodge.

Super Princess Peach
In Super Princess Peach, Rex will be flipped over if Peach stomps on it twice. Swinging Perry at one will take it outright.

Variations

 * Shroob Rex