Rex is a dinosaur that made his debut in Super Mario World. In the Mario and Luigi sieries he doesent appear on the field, just battle field.
Mario and Luigi Superstar SagaEdit
Rexes appear on hoho mountain, sometimes when Mario and Luigi enter a battle the rex is there to. The rex needs to be stomped on to make it shorter, or else its attacks are unavoidable.
Mario and Luigi Partners In TimeEdit
Rexes are brainwashed by the Shroobs, turning them into Shroob Rexes. A Shroob Rex is fought the same way as normal rex.