The holidays at Canterlot High are always lovely. Bells ring, children sing, and old friends reunite. Sunset and her friends are in good cheers when the Doctor returns for a visit. However, he discovers a crack in time leading to Equestria. Even when he closes it, the crack returns, and a swarm if Changelings comes out of it. With the TARDIS sent off who knows where, the Doctor is stuck between a rock and a hard place, as he must protect all of Canterlot High's students from the Changeling Invasion.

'Alternate Universe' tag for slight differences in the timeline.