The Zombies are undead monsters from the Regular Show TV series. who debuted in the episode "Grave Sights".
When the park decided to host a scary movie night at the old graveyard. They decide to watch Zombocalypse (3D) on an old Zetamax movie projector. After Rigby knocked the movie out of the projector and put the tape in upside down, a powerful electric blasts shoots through the projector and reanimates the dead people in the graveyard, turning them into zombies. They then emerge from their graves and try to attack the audience. Mordecai and Rigby, along with Skips, Muscle Man, and Hi Five Ghost try to defend the people by using Muscle Man's sports equipment to fight back the Zombies. Suddenly rising from graveyard came a super strong zombie named Howard Fightington who was too strong to be defeated. Until, Mordecai and Rigby drove a golf cart into him, ending the zombie attack. The audience then left happily, thinking the zombies were just part of the movie they were watching, including Benson.
The Zombies and Howard Fightington returned in "Exit 9B" as some of the many villains that were brought back to life by Garrett Bobby Ferguson Jr. They were eventually sucked back into the portal once Thomas signed the document.
- When they showed Howard and the Zombie from the movie, they showed them standing next to each other on purpose to show that they are very similar, as the antagonist of both fights.
- In "Exit 9B", Garrett Bobby Ferguson Jr. calls them, "Demon Spawn of the Underworld".
- The Zombies also screamed the famous Wilhelm scream in "Exit 9B".