Slim is the most frequently seen Killer Klown and one of the main antagonists in the film Killer Klowns from Outer Space. He is a thin Klown with orange hair that resembles Larry Fine’s hairstyle and wears a long pink suit.
Slim began his role in the alien invasion using shadow puppets. He was entertaining a group of people at a bus stop with shadow puppets including a rabbit, an elephant, George Washington and his crew on a boat crossing the Delaware River, a dancing lady, and then a Tyrannosaurus rex. Police Officer Hansen and Mike Tobacco, the film's protagonist, saw Slim use the Tyrannosaurus shadow puppet to swallow up his human audience. The helpless humans appeared as popcorn in Slim's hand which he then put inside a bag with hundreds of other pieces of popcorn, and their screaming voices were faintly heard. Mike became extremely terrified at this, trying to run over Slim with Officer Hansen's police car, but Slim was able to jump up the entire building where his shadow puppet was laid upon to avoid getting hit.
Later, Slim was seen pretending to use an incredibly fast, invisible motorcycle to knock a helpless driver off a bridge, causing his car to explode with Slim laughing maniacally.
Later on, after Debbie was running away from the Klown Offspring that had hatched in her bathroom, Slim imitated Mike's voice, saying "Debbie Debbie, it's Mike open up" tricking Debbie into opening the door, only to realize that it was Slim who was saying it. Debbie slammed the door but Slim began to knock it down, then Debbie tried to jump out the window only to find Bibbo, Rudy, Shorty and Chubby in firefighter helmets using a trampoline as an alternative back-up. Slim, by now inside the house, then grabbed Debbie, who was screaming while he laughed, and threw her onto her couch. Slim had used a device that encased Debbie inside a balloon, which was, possibly, so that they could turn Debbie into a female Killer Klown for sexual purposes, just like they have done with several other human women.
Mike arrived with the Terenzi Brothers in an ice cream truck to find the Klown Kar parked right next to the apartment building that Debbie lives in. Slim saw Mike behind him, recognizing Mike as the human who tried to ram him over for using the shadow puppet to swallow people. Slim had driven away inside the Klown Kar and faced a policeman who was refusing to let them access their Big Top headquarters, and the five Killer Klowns inside the Kar considered him as a pest. Slim, Shorty, Chubby, Rudy, and Bibbo took out their corrosive pies, throwing them at the police man who asked, “What are you going to do with those pies, boys?” which killed the police man. Slim then carried the balloon carrying Debbie inside and went into the Big Top. Slim was later seen with a bent golf-club like weapon trying to get Mike, Debbie and Officer Hansen, but he was distracted by the fake plastic head of "Jojo" on top of the ice cream van driven by the Terenzi Brothers, who ordered the Killer Klowns to halt their attack. When Klownzilla came in, Slim left along with all the other Klowns. He died at the end of the film when Klownzilla exploded, making the Big Top burst into flames.
- Slim probably killed hundreds of humans using the Tyrannosaurus shadow puppet and the scene where he was shown doing so to passengers waiting for a bus were among his last victims.
- Slim features prominently in the music video for the song "Killer Klowns From Outer Space" by The Dickies. In the video, he is arrested, fingerprinted, (his fingerprints are little happy faces), picked out of a lineup, and put on trial, presumably for murder, (immediately before the trial there is a flashback to the scene where Slim runs a driver off of a cliff, implying that he may have been charged with that particular murder). He is put in prison, along with Rudy, Jumbo, Spikey and several other Klowns. When the Klowns replace the band, Slim is seen playing a guitar alongside Jumbo. It appears he turns the tables on his captors, and in the end he throws the judge, (the band's lead singer), into a cell, and walks away.
- His hand is seen in the film's poster that shows him shattering the spinning planet Earth, which he is twirling like a basketball.
- The Halloween Costume Shop has officially released a costume of Slim.