After trying to warn her mentor, Princess Celestia, about the imminent return to Nightmare Moon, Twilight Sparkle in not pleased about being sent to Ponyville with orders to oversee the preparations for the Summer Sun festival. Even more frustrating, however, is having to foalsit Celestia's daughter, the rebellious Princess Rainbow Dash.

Princess Rainbow, meanwhile, just wants to devote her day away from the castle to goofing off and having fun with the common ponies, and she definitely isn't looking forward to spending time with her mother's pet egghead.

Twilight and Rainbow have known each other since they were fillies but are nothing alike. Can two so different ponies really ever be friends?