Fatso had orange hair and wore a blue/white polka-dot suit with a yellow, pink and blue frill. He is morbidly obese about his hands and face. He was seen giving a Valentine's Day card to a woman when The Klowns, including Shorty, Rudy, Bibbo and Chubby, were killing people door to door. The woman who got the card was so happy that she turned around, not noticing that Fatso was about to kill her with his cotton candy gun/hand puppet. Fatso is also the only Klown who had a very clear change in facial expression, from smiling to frowning before he killed the woman with his cotton candy gun. He was also seen when he, Spikey and the other Klowns are chasing Mike and the others through the Big Top. Dave shot him in the nose, causing him to explode off-screen.
The Halloween Costumes shop released a mask called 'Fatso'. The mask, though, is actually modelled from Chubby, with Chubby's hairstyle and blue frill collar, so, technically, it is misnamed.
There is another, unnamed Killer Klown mask based on Fatso.