His vocal sound effects were provided by Tony Lamberti.
Mayhem is a ghost haunting the Stonebrook Theater in New York City. In contrast to most of the other spirits who appear in the film, he is completely inhuman in appearance, resembling an enormous winged dragon or demon. He is green with glowing red eyes. The Ghostbusters get a call about an attack at the theater during a heavy metal rock concert, when something attacked the janitor in the basement, badly injuring him.
Arriving, they are directed into the basement. Patty Tolan encounters Mayhem first. He is possessing a female mannequin used for costumes and chases her until she finds her teammates. The possessed mannequin kicks the door in. Declaring she wants the ghost inside of the mannequin, Erin Gilbert fires at it with her proton stream. The other Ghostbusters follow suit, destroying the mannequin and revealing Mayhem who roars at them and flies away down the hall before going through the ceiling and into the rock concert going on upstairs.
Initially, everyone thinks he is a special effect, until the band's effects technician yells out that it's "not one of mine" and Mayhem hurls the lead singer of the band through a wall. Rushing onto the stage, the Ghostbusters battle Mayhem and eventually capture him, to thunderous applause from the audience. Later, however, paranormal debunker Martin Heiss stops by their headquarters and demands proof there is actually a ghost in the trap.
Abby Yates refuses, both because she doesn't care what Heiss thinks and because she is afraid of what will happen if she opens the trap. But the prideful Erin, eager to prove Heiss wrong, opens the trap. Upon being released, Mayhem hurls the terrified Heiss out of a window and then flies away. Following the Fourth Cataclysm created by Rowan North, the Ghostbusters must face Mayhem again, along with Gertrude Aldridge and the ghost of the executed murderer from the subway. They defeat all three.
- Mayhem strongly resembles the demonic minions from Anastasia, except he has red eyes while the minions have yellow eyes.
- The name "Mayhem" means violent or damaging disorder; chaos.