This creature is never called by a given name (like Bakhita or Lady Margaret). However, Robert Muldoon nicknames her "Rexy" on multiple occasions in the first novel. This is similar to how the Big One, a Velociraptor, is also based on a nickname and not a given name in the franchise. She might have also gotten this nickname from Billy Yoder, but under a different spelling ("Okay, we can't go back outside because of our old friend Rexie").
Rexy was born in 1990 inside the InGen Compound of Isla Sorna where she spent two months of her life inside the lab being taken care of by its workers before being transported to Isla Nublar to live in the Tyrannosaur Paddock as an attraction for InGen's Jurassic Park.
Isla Nublar Incident (1993)
When the inspection team constituting of vertebrate paleontologist Dr. Alan Grant, paleobotanist Dr. Ellie Sattler, chaotician Dr. Ian Malcolm, lawyer Donald Gennaro, and John Hammond’s grandchildren Lex and Tim Murphy took a tour of the Park, the Tyrannosaurus was initially a no-show. Although computer technician Ray Arnold attempted to lure her to her paddock fence by tantalizing her with a goat, however, Rexy still refused to answer the call. However, later that night, a tropical storm forced the tour to be turned around sometime after the group visited the Triceratops Paddock. Unfortunately, due to Dennis Nedry’s programming, the tour vehicles that the tour group were in shut down in front of the paddock with its electrified fencing also shut down. At this point, Rexy revealed herself to the visitors by eating the goat left by the fence as bait. Gennaro, in a fit of panic, left his tour car and ran to the nearby restroom hut for refuge. By that point, the Tyrannosaurus rex moved to the disabled fencing and ripped the fencing apart with her teeth; she proceeded to step through her mangled handy work and roar. After a minute or two of exploring and investigating the Explorers, her attention was was aroused by the light that was emitted from a flashlight Lex had activated in the front Explorer. Unaware that the source of the light was inside the car, she walked right to the front door and peered out into the jungle in front of the SUV. It was not until Tim slammed the open door next to the rex that she had discovered the source of the light. Now confident that the light was coming from inside the Explorer and that there were interesting objects inside, she set to attacking the mysterious vehicle in front of her, searching for a way to get at Lex and Tim. Thanks to the efforts of Dr. Grant and Dr. Malcolm, the T. rex was briefly distracted. Rexy followed fleeing Dr. Malcolm toward the Tyrannosaur Paddock Bathroom, injured him as he was flung into the building and ripped apart the cowering Gennaro while Dr. Grant rescued the kids inside the car. Before long, however, Rexy returned and pushed the vehicle over the cliff while Tim was still inside.
After Dr. Grant rescued Tim from the tree, the two with Lex, began their trek back to the Visitors Center, Park game warden Robert Muldoon and Dr. Sattler arrived at the Tyrannosaurus Paddock to retrieve those who had been stranded there only to find Rexy's mess. Acting quickly, the two began searching for the group and calling out their names. At the site of the collapsed restroom hut, Muldoon and Dr. Sattler found the remains of Genarro and recovered Dr. Malcolm who was injured, but alive due to his quick thinking to reduce blood loss by using his belt as a tourniquet. After loading Dr. Malcolm into their Jeep, the two took one last sweep of the area, Dr. Sattler spotted the ruined hulk of the second tour car that Rexy had pushed over the cliff adjacent to her Paddock. Although Muldoon and Dr. Sattler did not find Tim, Lex, or Dr. Grant, they did find their shoe prints in the mud, which told they were alive. When the two returned to the guest jeep, Rexy crashed through a line of trees and began chasing the three along a service road. After a very close chase, the Tyrannosaurus was unable to pin down her prey and so gave up her pursuit.
Sometime during the night of the tropical storm, after escaping her paddock, Rexy began wandering farther from her paddock area. As Dr. Gerry Harding and his daughter, Jess Harding, were heading for the boat to the mainland after Gerry returned to the site of the sick Triceratops to pick up Jess in his gas powered jeep, they found Nima Cruz, a corporate spy. Nima had been one of the contacts that Nedry was supposed to deliver the stolen embryos too. When Nedry did not show up at the East Docks, she went looking for him but encountered the juvenile Dilophosaurus instead. As the three made their way, they come across an infant Triceratops that was out of her paddock. The trio managed to get the dinosaur back into her enclosure, but Lady Margaret, the alpha female, appeared and attacked, which also attracted Rexy. The group barely managed to escape, hiding in a maintenance shed as the dinosaurs fought, and decided to spend the night inside. Rexy, meanwhile, returned to near her paddock.
The next day, as Grant’s, Tim’s, and Lex’s trek continued, they found themselves in the Gallimimus Enclosure, and witnessed Rexy hunting the herd of Gallimimus. After watching in amazement for a while from behind a fallen log, Lex begged Dr. Grant for them to go, to which Grant obliged. However, Tim continued to stare in fascination and so had to be forcibly taken away by Dr. Grant.
Rexy was seen later that day when she had come through the hole in the wall, and grabbed a Raptor from mid-air just as it was to pounce on the humans and crushed it in her jaws. Using the distraction, Rexy provided, the humans fled. Meanwhile, the Raptor that had pursued the group through the Visitors Center foolishly attacked the larger theropod. Rexy snapped at her but could not reach her. Rolling her head, the Raptor fell into the T. rex mouth where she was killed and then thrown against the Tyrannosaurus skeleton and Rexy let out a mighty bellow. Afterward, Dr. Gerry Harding, Jess, and Nima Cruz reached the Visitors Center unaware that the surviving cast of the movie had just recently fled the island. Once inside, Dr. Harding heard a radio trying to contact them. Locating it, he spoke with Dr. Laura Sorkin, who helped cure Nima of her ailment caused by a Troodon bite. Rexy attacked once again, forcing the trio to avoid her as best they could, eventually managing to lure Rexy away with the help of the tour vehicle. After a second mercenary team landed on the island to rescue those who had been left behind and retrieved the survivors, the group headed back to the helicopter but found that the mercenary Danny Cafaro had disappeared. Rexy reappeared and made her way towards them, forcing Oscar Morales to fix the chopper himself. They managed to get into the air just in time. After a failed attempt at rescuing rogue genetic scientist Dr. Laura Sorkin from her research lab on the north end of Isla Nublar, the group made their way to the North Dock, the trio eventually met up with mercenary Billy Yoder at the shipping dock entrance. A confrontation ensued with Nima getting into a scuffle with the mercenary. During the conflict between the two, Rexy stalked into the shipping yard forcing all four of the humans to freeze in their positions. Rexy started to sniff at Jess when her father gently nudged the cryocan with his foot causing it to roll toward the dock’s edge. In a momentary lapse of judgment, Yoder scrambled to save the can before it fell into the water. Although he had saved the can, he had caught the attention of the large theropod. Rexy only hesitated a moment before it engulfed the man with its jaws and lifted him in the air to consume him. Yoder dropped the can. With the T. rex back turned to them, Nima raced to retrieve the can, the Hardings followed closely behind. Rexy was alerted by the movement behind her and chased after them. Nima and Jess squeezed into shelter while Dr. Harding was left outside. Dr. Harding then attempted to distract Rexy in order to keep its attention away from the two ladies. The T. rex damaged the bridge platform the pair was standing on flinging Jess over the edge. She managed to keep herself from falling off the bridge together but was dangling mere feet from Rexy. She pleaded for Nima’s help and was saved from the jaws of the predator at the expense of the cryocan that was crushed by the approaching Tyrannosaurus. Dr. Harding, while Rexy had turned to face Nima and Jess, grabbed a steel pipe. He swung the pipe into the leg of the Tyrannosaurus, successfully gaining her undivided attention, thus allowing his companions to escape to the last remaining boat at the end of the docks. Dr. Harding scrambled through the container yard, the large theropod hot on his heels. Dr. Harding eventually found cover inside an animal cage. Rexy could not reach the man with her jaws due to the small opening at the end that was suited for caging smaller, man-sized dinosaurs. Frustrated, the animal thrashed about and finally flung the cage toward the pier that the small boat was located.
Dr. Harding noticed that he was less than a one hundred meters from salvation, he scrambled to his feet and sprinted for the boat that his daughter was pull-starting. Rexy stalked through the gate that separated the pier from the container yard. The animal was nipping at Dr. Harding for the final stretch As he neared the end of the dock, he jumped onto the moving boat as the carnivore made one last effort to grab him. The boat successfully swept its three passengers away from the angered animal that bellowed loudly after its prey.
In the aftermath of the incident, Rexy went wild and lived on Isla Nublar for about a decade,probably surviving off any of the herbivorous dinosaurs that managed to survive the incident.
Sometime before or after the construction of Jurassic World, Rexy was put back into captivity and lived in the T. rex Kingdom attraction of the dinosaur park. She is still fed goats like before, but to bring her out, they throw in a flare to get her attention.
Similar to the Raptors, Rexy also played a protagonist role in the film, however, Rexy mainly stayed in her paddock for most of the incident, though she became involved when Claire Dearing told Lowery Cruthers to open her enclosure's door after Claire's nephew Gray Mitchell told her that there needed to be another dinosaur to help kill Indominus rex during the final battle of the incident. Using flares, Claire guided Rexy to the Indominus rex where she threw the flare at the hybrid. When the flare hit the I. rex, Rexy attacked her viciously. Initially Rexy had the advantage, landing several blows and drawing first blood on the I. rex, but the hybrid soon became the dominant opponent in the conflict, putting the Tyrannosaurus to the ground. However, before the Indominus could kill her, Blue, the surviving Velociraptor of the battle, intervened by lunging onto the I. rex, giving Rexy time to get up off the ground. With Blue latched onto the hybrid Rexy grabbed the Indominus dragging her into the nearby buildings of Main Street. She finally flung the hybrid near the edge of the Jurassic World Lagoon where the Mosasaurus that resided there leaped out of the water to snatch the I. rex, killing the hybrid. After the fight, Rexy and Blue looked at each other, but Rexy decided to spare Blue, thanking the raptor for her help before walking away, wild once more. She later let out a triumphant roar from the Control Center hela pad while surveying the ruined park.
Behind the scenes
Rexy's animatronic in Jurassic Park would occasionally malfunction in the rain.
The original ending to Jurassic Park did not feature Rexy at all unlike the final film. The Velociraptor pack would have either just been killed by the two mounted skeletons inside the Visitor Center collapsing on them or gunned down by Robert Muldoon. Director Steven Spielberg scrapped this ending because he realized that Tyrannosaurus rex was one of the stars of the film only rivaled by Velociraptor.
A Jurassic World sight gag is shown where Rexy destroyed the Main Street's Spinosaurus skeleton to kill the Indominus, referencing the fight in Jurassic Park \\\ where a Spinosaur killed a T. rex and the scene's backlash. Colin Trevorrow probably put this in to show apologies to T. rex lovers, even though he didn't direct Jurassic Park \\\.
- Rexy will meet Thomas, Twilight, and their friends in Thomas and Twilight Sparkle visit Jurassic Park and see them again in Thomas and Twilight Sparkle visit Jurassic World.
- Rexy will meet the Eeveelutions' in The Eeveelution Family visit Jurassic Park and meets them again in The Eeveelution Family visit Jurassic World.
- Rexy will meet Winnie the Pooh and the gang in Winnie the Pooh Goes to Jurassic Park and see them again in Winnie the Pooh Goes to Jurassic World.
- Rexy will meet Tino Tonitini in Weekenders visits Jurassic Park and see them again in Weekenders visits Jurassic World.