|Species :||Tyrannosaurus Rex|
|Time period :||Late Cretaceous 65 million years ago|
|Primary diet :||Carnivore|
|In the series|
|Appearances :||End Game|
Jack Palance (or simply Jack), was an aggressive male T. rex (probably the name was unmentioned in the episode) who won the first battle with Stumpy and the main antagonist of "End Game". He later attacked and cannibalistically killed his rival's young after they strayed too far from their parents. He also tried to take a Triceratops carcass from his enemies, but after a fight, the two T. rexes pushed him down and he was impaled on the horn of the Triceratops.
He was greyish-brown with white pits and divots on his skull and was red eyes. And if seen closely, is a bit more muscular than his rival.
- Jack is noticeably more aggressive than his "heroic" counterpart Stumpy, seemingly intentionally antagonizing him and Tinkerbelle throughout the episode.
- Jack has a small defect in the vertebrae, so he often cracks the bones of his neck.