A Regular Epic Final Battle

Before the episode's events, Pops is upset about the upcoming fight with his evil brother Anti-Pops and is in a terrible mood. The gang at the park cheer him up by throwing him a party. All of their memories are put onto a collection of Blu-rays and buried in the park to remember the events. They set a course to the location of the fight, Lolliland, Pops and Anti-Pops' home planet.

Pops has a nightmare about his fight and Mordecai and Rigby comfort him. A short time later, the park crew arrives at Lolliland. They meet a group of Lolliland natives: Frivola-Kranus, Quadravi-Kranus, and Weird Mushroom Guy. The natives explain Pops and Anti-Pops are named Mega-Kranus and Malum-Kranus, respectively. The natives show the park crew ancient tapestries of the previous battles between Pops and Anti-Pops, which detail prior incarnations of the park crew fighting alongside Pops.

Knowing that all of the prior battles have ended in a stalemate (resulting in the universe resetting), Mordecai comes up with setting traps for Anti-Pops to give Pops an upper hand, which he didn't have in previous battles. Pops reluctantly agrees to do so.

After Anti-Pops and his bounty hunters arrive in an Uber-like taxi, Pops tries to convince him not to fight due to them being brothers. Anti-Pops refuses and attacks Pops but is caught in the traps laid by the park crew. The victory is short-lived, however, as Anti-Pops quickly escapes the traps.

To ensure his friends' survival, Pops makes a deal with Anti-Pops: whoever lands the first blow in battle gets to decide the fate of the universe. Pops successfully injures Anti-Pops, but Anti-Pops breaks the agreement and continues the fight. Meanwhile, the park crew, HD DVD, Blu-ray, the Baby Ducks, Toothpick Sally, Recap Robot, Chance Sureshot (whose prior "death" is revealed to be that of a clone), the Guardians of Eternal Youth, Gary, Carter and Briggs, Death, Party Horse 42699, and the Guardian of Lolliland (who is supposed to remain neutral) fight against Anti-Pops's minions and Streaming Modem and defeat them.

However, Anti-Pops unlocks his full power and begins erasing Lolliland. The erasing of Muscle Man and Hi Five Ghost causes Pops to unlock his full power. Anti-Pops proceeds to erase the rest of Pops' allies and friends except Mordecai and Rigby, and kick his brother into a portal. Mordecai and Rigby realize that the only way to stop time from resetting is to get in between them while they are about to punch each other. As the two brothers' punches collide (with Mordecai and Rigby between their knuckles), it obliterates the entire universe and resets time.

Part 3 begins precisely like the first episode of Season 1, "The Power," seemingly "resetting" time back to the series' beginning. However, Rigby quickly remembers the events of the prior episodes and the rest of the series. However, Mordecai does not remember, so Rigby shows him the stash of buried Blu-rays, which triggers his memories of the series' events after touching it. Realizing that time didn't correctly reset, they use the Power to take them to the future and back to the battle between Pops and Anti-Pops. Anti-Pops attacks them, destroying the Power in the process. As Pops continues to fight, it becomes clear that fighting Anti-Pops will inevitably lead to another stalemate, which he realizes through flashbacks to the first two parts of the episode and "Kill 'Em with Kindness." (The scenes where Pops tries to attack Anti-Pops show several post-its notes that deal with the scene discussions that the writers have had earlier. It includes artist drawings, dialogue boards, and the letters from "Regular Show" also appear in the background. Purposefully, the show's creators did this to break the fourth wall and add experience and memory to its viewers.)

Pops grabs Anti-Pops and flies toward the sun, telepathically comforting Mordecai and Rigby. Anti-Pops reconciles with his brother, and the two are finally at peace before they fly into the sun. With the resetting cycle broke, the effects of Anti-Pops' erasing are reversed, and the erased workers (and allies) are revived. After three years in space, the park workers fly back to Earth, where they reunite with their friends and families and are welcomed as heroes.

The park workers and Mr. Maellard erect a memorial statue in honor of Pops and mourn him. After six years of working at the park, Mordecai and Rigby quit their jobs and move on with their lives. Mordecai becomes a successful artist, marries a bat named Stef, and has three children with her. Rigby marries Eileen and has two daughters with her.

Muscle Man and Starla move into a better trailer in the park and have many children, who adopt many of his mannerisms (like taking off their shirts and yelling). High-Five Ghost and his girlfriend, Celia, become party DJs touring in Prague and later have a son. Benson, who has now become the park owner after Mr. Maellard passes away, reunites with and marries his girlfriend Pam (who becomes co-manager alongside her husband) and the two adopt four cats along with Applesauce, Benson's pig. Skips continues happily working in the park but ditches his trademark jeans for jean shorts.

At their 25th anniversary reunion, the park crew raises a statue of Mr. Maellard next to the one of Pops and take a picture in front of it with their families. As the reunion party commences, Mordecai and Rigby (now 54-years-old) reminisce on Pops' sacrifice and how none of them would have been able to lead such beautiful lives without him. They decide to play some old arcade games in the shed before saying their catchphrases one last time and laughing at how immature they used to be. This episode ends with the revelation that Pops is watching his friends in what seems to be an afterlife (presumably Heaven) on a VHS tape labeled "Regular Show." He ejects the video and says "Jolly good show" as the series officially ends set to the 1977 David Bowie song "Heroes".