In "Party Line" the evil dinosaur appears near the beginning of the episode, where it attempts to attack Mario, Luigi, Yoshi and Princess Toadstool. Before the evil dinosaur can eat them though, Mario, Luigi, Yoshi and Princess Toadstool manage to evade the evil dinosaur by hiding behind a rock.
The evil dinosaur appears later in the episode rampaging through Dome City, which is nearly defenseless due to the Cave People being too busy gossiping on their new phones to fight the evil dinosaur off.
Having Luigi and Princess Toadstool run off to warn the Cave People of the evil dinosaur, Mario goes to fight the ferocious dinosaur himself. Tugging on the evil dinosaur's tail right before it's about to devour Oogtar, Mario manages to get the annoyed evil dinosaur to chase him.
Running after Mario, the evil dinosaur is bashed in the chest when Mario bounces through the air after running into and bouncing off a vine. Though winded, the evil dinosaur tries to lunge at Mario, who jumps out of the way, causing the evil dinosaur to fall to the ground. Getting-up, the evil dinosaur sees Mario hitting several ? Blocks looking for an item to help him in battle. Unfortunately for Mario, all he gets from the ? Blocks are coins, which Mario feebly throws at the evil dinosaur. Eating these coins, the evil dinosaur quickly spits them out and throws one at Mario's head, making the him dizzy.
This coin bounces off Mario's head and hits a nearby ? Block, which releases a feather. A disoriented Mario tries to grab this feather, but fails and falls to the ground. On the ground, Mario grabs a Starman from above his head, which he uses to become super-powerful.
With his newfound super-strength, Mario grabs the evil dinosaur by the snout and launches it into space, where he continually soars, never to be heard from again.
It is later revealed in the episode "Mama Luigi" that Luigi and Yoshi had met the evil dinosaur before. Shortly after finding the recently hatched Yoshi, Luigi is attacked by the evil dinosaur and its turquoise friend, also a Tyrannosaurus rex, in the Lava Pits.
Thinking Yoshi to be the baby of the evil dinosaur and its friend, Luigi tries to hand Yoshi over to the two dinosaurs. Luigi quickly grabs Yoshi away after the evil dinosaur tries to eat him. An enraged evil dinosaur tries to eat Luigi, who narrowly escapes the evil dinosaur and its friend by jumping across a river of lava with Yoshi.
The evil dinosaur also appears in the opening and ending sequences of Super Mario World; here, the evil dinosaur, after crushing a Cave Person's car, attempts to eat Luigi, who is saved just in time by a vine-riding Oogtar. They are both voiced by Dan Hennessey, who also voices Bully Koopa and Rockman.