After the events of "Ice Age: The Meltdown", life begins to change for Manny and his friends: Scrat is still on the hunt to hold onto his beloved acorn, while finding a possible romance in a female sabre-toothed squirrel named Scratte. Manny and Ellie, having since become an item, are expecting a baby, which leaves Manny anxious to ensure that everything is perfect for when his baby arrives. Diego is fed up with being treated like a house-cat and ponders the notion that he is becoming too laid-back. Sid begins to wish for a family of his own, and so steals some dinosaur eggs which leads to Sid ending up in a strange underground world where his herd must rescue him, while dodging dinosaurs and facing danger left and right, and meeting up with a one-eyed weasel known as Buck who hunts dinosaurs intently.

When Sid accidentally destroys Manny's heirloom Christmas rock and ends up on Santa's "naughty...

When Sid accidentally destroys Manny's heirloom Christmas rock and ends up on Santa's naughty list, he leads a hilarious quest to the North Pole to make things right and ends up making things much worse. Now it's up to Manny and his prehistoric posse to band together and save Christmas for the entire world.