Matilda made her debut in T-Rex Returns. When Nigel Marven finds Terrence & Matilda, they are both half-starved. Their mom was about to feed them an Ornithomimus carcass, but a male Tyrannosaurus Rex showed up. He wanted the carcass, but the mom wouldn't allow it. The two adults engage in a huge, violent fight. Matilda & Terrence both stay hidden, for if the male notices them, they would most likely be killed. It is a long fight, but their mother ends up losing the battle, and is knocked to the ground. She gives off one final roar, before succumbing to her injuries. The two babies are now orphaned. Miles away, the meteorite hits Earth. The deadly shock wave is only three minutes away from where they are. Nigel tries lure the two T-Rex with the only thing he has: a sandwich containing meat. The two dinosaurs hesitate at first, but then they both made a lunge for the sandwich (or more likely Nigel). And as the shock wave approaches...Terrence & Matilda are both rescued! They are then fed in the observation pens before being put into T-Rex Hill. Once there, Terrence & Matilda are given their names. It isn't all cute though; the two Tyrannosaurs will double their weight every year until full-sized, turning Matilda & Terrence into the most dangerous killing machines in 65,000,000 years. Let's all hope Prehistoric Park knows what tussle it just put itself into!
In A Mammoth Undertaking, Matilda & her brother are making up for their starved conditions in the previous episode. T-Rex babies grow quickly; they will grow until they are as long as a double-decker bus and weigh five tons! The two T-Rex are just polishing off huge amounts of meat. Later, during feeding time, The two Tyrannosaurs are still putting on weight.
In Dinobirds, Terrence and Matilda have both grown tremendously in size. While Nigel is off rescuing a Microraptor, the two T-Rex are at each other's throats. Bob and the team need to separate them, or there will be a fatality. The team fires a high pressure hose at the theropods to split them up. The fight ends, but Terrence & Matilda must be separated for their own good. They are both put into holding pens, while the team constructs a dividing wall in T-Rex Hill. Both Tyrannosaurs are disappointed with their new living arrangements.
In Saving the Sabretooth, the dividing wall has been completed. Matilda & Terrence are put back into the enclosure. As Terrence approaches Matilda's half, she greets him with a hostile lunge. It appears that the wall could be a life-saver for Terrence. (Just wait.) The level of danger increases at the park, as Matilda shows no sign of calming down.
In The Bug House (episode), Nigel heads to the park to prepare for his arthropod-rescue mission, but is alerted by Bob to head to the T-Rex enclosure. Matilda has just broken into Terrence's enclosure! Terrence wants Matilda to leave. The two then Tyrannosaurs engage in combat. Being the larger & more aggressive of the two, Bob tranquilizes Matilda first. The dart hits, but there is a problem: tranquilizers take time to work on reptiles. As Terrence tries to ready another attack, Matilda headbutts him to the ground. T-Rex are known to have been cannibalistic. For Terrence, the dart may have come too late. Nigel then drives in, and Matilda follows him instead. Nigel leads her to some trees. As Matilda pulls back the cover on Nigel's jeep, she sees that he is gone. Nigel climbed up a tree, and stays there until she is fully sedated.
In Supercroc, Matilda was one of the animals to escape in the Mass Break-Out. She was also portrayed as the main antagonist of the break out as well. After making her escape, Matilda catches the scent of food, and goes hunting. When Bob is seen trying to round up some of the Ornithomimus and the Elasmotherium, Nigel alerts him that Matilda is right behind him, and he must flee. Being spooked by the T-Rex, the Ornithomimus & Elasmotherium make a break for it, and almost trample on Nigel. Matilda heads for the elephant herd, and has singled out the one calf of the herd. Suddenly, Martha cuts off Matilda's path to protect the calf. Nigel manages to lure Matilda away from Martha, and the two go into a chase. They run past Theo, a group of Nile Crocodiles, and the Deinosuchus, where the giant crocodile lunges out of the water to attack Matilda. The attack slows her down, and gives Nigel more of a lead. Ultimately, Nigel is able to lead her to the holding pens, and Matilda is finally contained.