Not much is revealed about the Tyrannosaurus Twins, not even their real names. One of the Tyrannosaurus Twins is extremely large and green, with red stripes on his face while the other is small, orange and has hair.
After being forced into a wrestling ring by Bowser to fight the Tyrannosaurus Twins, Mario is approached by the larger, green Tyrannosaurus Twin. Feigning kindness by trying to get Mario to shake his hand, the green Tyrannosaurus Twin proceeds to grab Mario and twirl him around in the air when the plumber does try to shake the dinosaur's hand.
Watching helplessly as his brother is pulverized, Luigi is sneak-attacked by the orange Tyrannosaurus Twin, who proceeds to grab Luigi and toss him through the air, where he collides with Mario. The Tyrannosaurus Twins subsequently bodyslam Mario and Luigi, pinning them to the ground.
It is only through the aid of Princess Toadstool and Yoshi that Mario and Luigi manage to get free from underneath the Tyrannosaurus Twins; having hit a ? Block, Princess Toadstool released a swarm of miniature Marios, which proceeded to cause havoc, distracting the Tyrannosaurus Twins.
Having gained a Cape Feather, Mario transforms into Cape Mario and proceeds to fling the green Tyrannosaurus Twin through the air with his newfound abilities. After having beaten the green Tyrannosaurus Twin, Mario aids Luigi in pinning the orange Tyrannosaurus Twin to the ground, defeating him and apparently knocking him unconscious.
The Tyrannosaurus Twins were apparently crushed under the debris of Bowser's collapsing television set-like structure when Yoshi weakened the structure's support by eating pieces of it.