Jumbo was the first Killer Klown to appear in the film. His shadow is seen on the circus tent and he snatched away the farmer's dog Pooh Bear with a net. The farmer was outraged that Pooh Bear has been abducted and angrily tried to sabotage the tent but got electrocuted doing so and was knocked onto the ground. Jumbo spotted him and killed the farmer with his cotton candy gun who was investigating the Big Top.
Later, Jumbo showed up at the mini-golf course outside of Polar Ice Burger was using a finger gesture to tell a girl to come close to him while holding a mallet behind him so he could kill her. However, the girl’s mother told the girl to finish her food before meeting Jumbo, which made the Klown get mad. It is unknown whether Jumbo decided to continue waiting and got the chance to kill her. Unlike the other Killer Klowns, Jumbo is very patient at using methods to kill humans and does not immediately attack them. In any case, he also seeded the restaraunt's dumpster with popcorn, which grew into Klown Offspring and killed at least one employee.
Jumbo had shown up at the Police Station where he was bothering Officer Mooney with his water squirt flowers, making Mooney decide to arrest him. Jumbo has an unlimited number of hands, as he removed the pair that Mooney handcuffed. Jumbo was ordered to walk inside the prison cell with the two teenagers arrested for alcohol use at campus. Mooney ordered Jumbo to get his hands out, then Jumbo popped out a new pair out of his sleeves then wiggled his hands behind Mooney when he was opening the cage. Mooney then said, "Get in there" and Jumbo skiddled in. Mooney used his baton to slap Jumbo on the back of his neck, Jumbo turned his head around and got mad at him. Mooney locked up the cage stating that Jumbo will be begging for mercy, then Jumbo used a white and red striped blow piece that popped out a hand which strangled Mooney to death. One of the prisoners asked Jumbo, “What are you in here for?”. Officer Hansen arrived at the police station and found the two prisoners covered in cotton candy cocoons which was Jumbo’s work. Jumbo had turned Mooney into his ventriloquist dummy while sitting on Mooney's chair. Jumbo also smudged blood on Mooney’s cheeks and made straight lines of blood on his mouth to make him look like a wooden puppet. Jumbo used Mooney as a puppet to speak in Mooney’s voice, “Don’t worry Dave. All we want to do is kill you”. Jumbo then released his hand covered in blood out of Mooney’s body and dropped it onto the floor. Jumbo shoved away the desk so he can proceed to kill Hansen. Hansen grabbed out his pistol shooting at Jumbo, which had no effect on him except at his nose as Jumbo kept walking towards him. Jumbo’s nose was shot, making him spin around in a green flash until exploding. He was the first Killer Klown to be killed by a human.