A mysterious new enemy, Anti-Pops, is after Pops forcing everyone on the Space Tree Station to evacuate.

Earl, an ancient sensei, begins training Pops for his fight with Anti-Pops, but Pops is not sure if he can or should go along with it.

Earl begins training Pops through the technique of the training montage which allows trainers to bend space and time while leveling up. Mordecai and Rigby use one of their songs to help Pops and end up trapping the Park crew in a montage.

Despite all of his training, Pops still does not want to fight, so he sets up a meeting with Anti-Pops to settle things peacefully.

The crew arrive on Planet Nielsen where they are reunited with the Guardians of Obsolete Formats and meet the Seer who has been watching them since the very beginning.

The crew arrive at Lolliland early, so they set up traps for Anti-Pops. Things seem to go off smoothly, but Anti-Pops is unfazed by their futile attempts.

Allies from both sides rally together for the epic fight. However, Pops and Anti-Pops are once again at a stalemate. Mordecai and Rigby are forced to jump between the two factions.

Mordecai and Rigby relive the first episode, but soon realize that they need to help Pops. Pops realizes that he must reach out to Anti-Pops and finally saves the universe at the cost of his life. The entire park crew return home to their friends and family where they are seen growing up and moving on to better lives. 25 years later, the entire crew return and Mordecai and Rigby reflect on Pops' sacrifice. Regular Show ends with Pops watching the series on VHS and uttering one final "Jolly Good Show".