Wuya brought the T-Rex to life by using the Rio Reverso on a massive oil drum. By feeding it sugar cubes, Wuya was able to control her and used her to attack the Xiaolin Monks. This attack was interrupted by Chase Young, who was upset that Wuya went behind his back to get the Shen Gong Wu. Chase Young used the Eagle Scope to increase the T-Rex's intelligence, and she immediately turned on Wuya.
After beating Wuya and Jack, knocking both of them into the water, T-Rex turned on the Xiaolin monks, whose attacks proved ineffective against it until Kimiko used her Wudai Fire Shield, which combined with her own deflected attack, causes the oil drum to explode. T-Rex runs towards the Rio Reverso, planning to create more dinosaurs, but ends up in a Xiaolin Showdown with Raimundo, playing "Jurassic Chess". Though both of them play quite well, Raimundo manages to win.
Prior to gaining intelligence, the T-Rex was a mindless, aggressive animal, simply working for Wuya. Though she recognized Chase Young in his reptilian form, and acted affectionately towards him.
After gaining intelligence, she speaks with a British accent, and talks like a stereotypical British gentleman. Though she is mostly looking for a decent bite to eat. During the game of chess, she shows her intelligence and familiarity with the game, recognizing many of the moves.
The T-Rex is a large greenish dinosaur. Her eyes change when she gains intelligence - initially, they appear mostly black with yellow pupils, but they look more human-like, but with a more yellowish color, when she gains intelligence.
Powers and Weaknesses
The T-Rex is large and physically very strong, able to resist most of the Shen Gong Wu attacks used against her. She is also quite intelligent after being hit with the Eagle Scope, evidenced by her chess skills.
Initially, the T-Rex is loyal to Wuya, and she is rather affectionate towards Chase Young in his reptilian form. But after gaining intelligence, she is only loyal to herself, seeing everybody else as just a bite to eat. Though she seems to show some respect for Raimundo's chess skills during their showdown.