William Trundle is a kind, dinosaur-obsessed boy who uses a wheelchair. As Christmas approaches, his greatest wish is for a real dinosaur. Far away at the North Pole, Santa and his elves discover a frozen dinosaur egg—leading to the birth of a unique creature: the Christmasaurus.
 
Their worlds collide on Christmas Eve when a magical mix-up sends the Christmasaurus to William’s house. Together, they embark on a wild, heartwarming adventure involving flying reindeer, a grumpy hunter named the Hunter, and the power of believing in the impossible.