Contains spoilers for this episode and earlier episodes.
Dipper feels crowded out of the attic when Mabel keeps inviting Candy and Grenda for sleepovers. After a particularly frustrating night, he asks for a room of his own. Soos discovers an unused bedroom in the Shack, but Mabel wants it too, and Stan makes them compete for his approval. The twins try to earn points through chores and helpful behavior until static from the bedroom's shag carpet causes them to switch bodies. Each now has a chance to sabotage the other by behaving badly in front of Stan. Their private contest spreads when Soos and Waddles also exchange bodies, creating problems well beyond the bedroom.
Dipper has to endure Mabel's sleepover in her body, while Mabel faces Stan's uncomfortable advice in Dipper's. Further swaps bring their friends, Stan and the police into the confusion. During the scramble for the room key, Dipper admits that he never really wanted to leave Mabel. He missed spending time with her and felt left behind by her new friendships. Mabel understands, and their competition ends once they speak honestly instead of trying to win. Everyone returns to the proper body, and Dipper gets the new bedroom with the carpet removed. Alone at bedtime, he asks Mabel for a sleepover. He eventually gives the room to Soos, choosing to share the attic with his sister again.