Regular Show Season 4 (2010) Episodes & Character Maps

Key story beats

Brainwashed Park Crisis — Mordecai and Rigby are the only ones able to save their brainwashed friends and the park.
Thomas Gets Targeted — Mordecai and Rigby try to stop Muscle Man from messing with Thomas.
Halloween Scary Stories — The group tells scary stories while traveling to a Halloween party; the stories include a haunting, an aging haunted bus, and a dangerous wallpaper man.
Honest Pie Judging — Mordecai and Rigby seek to judge a pie contest and discover that the role requires honesty.
Benson Attempts a Drum Solo — Benson tries to prove that he can perform an advanced, extremely long drum solo.
Muscle Man Hides Bald Spot — Muscle Man tries to conceal his bald spot from Starla during their first anniversary.
Pops Faces a Chugging Challenge — Pops attempts to prove he is one of the guys by completing a milk-chugging challenge, which leads him to a strange place with white creatures.
Rigby Trains for a Pull-Up — Rigby struggles to do one pull-up during the employees' physicals and must find a way to succeed or risk being fired.
Magical Present Threatens Christmas — Mordecai and Rigby must destroy a magical present and save Christmas from one of Santa's elves.
Farewell at the Ballroom — The group plans a going-away party for Margaret, but the deceased ballroom owners refuse to keep the room clean while waiting for a girl who never arrives.
Firework Emergency — After Muscle Man accidentally sets off fireworks intended for the park celebration, the group travels to a factory to obtain a powerful replacement and avoid being fired.
Weekend Relationship Test — Starla asks Muscle Man to avoid contacting her for a weekend to test their relationship, a challenge neither finds easy.
Search for a Deadly Sandwich Cure — After Benson becomes ill from a deadly sandwich, Mordecai and Rigby have six hours to find a cure with help from the Death Kwon Do sensei.
Searching for a Frontman — Mordecai and Rigby try to reunite a rock band after suspecting its presumed-dead frontman is living at the park.
Bet to Kiss Margaret — Mordecai bets Muscle Man that he will kiss Margaret by Friday at midnight or wear a diaper for a week.

Character relationships in season 4

Mordecai / Hi Five Ghost — Best friends and coworkers — Rigby: Mordecai and Rigby are close friends and park coworkers whose schemes and emergencies frequently bring them together.
Benson / Pops / Muscle Man — Romantic partners — Starla: Muscle Man and Starla are a couple whose relationship is directly tested in the season.
Mordecai / Hi Five Ghost — Romantic interest — Margaret: Mordecai has romantic feelings for Margaret and repeatedly tries to make a romantic advance.
Benson / Pops / Muscle Man — Coworkers — Rigby: Rigby and Muscle Man work at the same park and sometimes cooperate, while Muscle Man's behavior can create trouble.
Rigby — Coworkers — Benson / Pops / Muscle Man: Rigby is a park employee whose work and misadventures involve Benson and the other park staff.
Mordecai / Hi Five Ghost — Coworkers — Benson / Pops / Muscle Man: They share park employment, with their work sometimes involving conflicts over Benson's expectations.
Mordecai / Hi Five Ghost — Friends — Eileen: Mordecai and Eileen cooperate as friends in organizing Margaret's farewell.
Rigby — Employee and employer — Mr. Maellard: Rigby is involved in an incident that puts Mr. Maellard's property at risk.