Theo

Theo is an adolescent male Triceratops that was rescued in T-Rex Returns. He was Prehistoric Park's first ever dinosaur, and prehistoric animal overall.

T-Rex Returns
Theo made his debut in T-Rex Returns, where he was first seen feeding on foliage when an injured female Tyrannosaurus tried to attack him. Seeing a rescue opportunity, Nigel thought he could rescue two species for the price of one, by using Theo to lure the Tyrannosaurus rex back to Prehistoric Park. Unfortunately, the Tyrannosaurus didn't take the bait and remained in the Cretaceous while Theo, on the other hand, went through the portal, and was declared the park's first ever prehistoric creature. After arriving at the park, Bob eagerly transports Theo to his new enclosure, Triceratops Creek. Later on in the episode, Bob watches the monitors in the control room, and notices Theo charging into a tree in his enclosure. Bob and Suzanne both head down to see what is troubling the Triceratops. Suzanne notices that Theo's frill has changed color, and believes that he is experiencing a surge of testosterone. This gives Bob an idea and he devises a plan to calm down Theo. After Nigel returns from his second rescue attempt, Suzanne tells him to check out Theo. As the two observe Theo, he charges right at them, only to be stopped by the fence. Like Suzanne, Nigel believes that Theo is experiencing a testosterone surge, by comparing Theo to a time when Nigel hand-reared a female baby fox that grew little aggressive as it matured. Suddenly, Bob shows up on a tire-padded tractor made to look like a Triceratops. As he drives up to them, he tells Nigel to hop on and tells Suzanne to open the gate. Bob and Nigel then enter the enclosure and joust with Theo, until the adolescent dinosaur has calmed down. Theo was then able to settle in.

Supercroc
In Supercroc, Theo wasn't focused on much, but was doing well in his enclosure. Unlike many of the other animals, Theo doesn't participate in the Mass Break-Out, but he did witness Nigel get chased by Matilda.

Two Triceratops were in the park in the opening titles even though Nigel never brought more than one back to the park in the original series, implying that after the events of "Supercroc", he rescued one more Triceratops for Theo.