The Cutie Mark Crusaders feel like they aren't being taken seriously by anypony because they are children. To prove themselves, they join the Mane Six on a new adventure to the town of Bikini Bottom where they meet a very energetic talking sponge
The Mane Six and Spike, along with Gabby and Gilda, are transported to the time of the Ice Age to help a mammoth, a sloth, and a saber tooth tiger return a human baby to his people.