Almost certainly the most well-known evil clown (save for Batmans archnemesis, the Joker; more on him later), Pennywise is modeled after real-life serial killer John Wayne Gacy, aka Pogo the Clown, a.k.a. "The Clown Killer." Gacy was convicted of sexually assaulting and killing 33 boys in 1980; he posed as a clown ...

The IT character Pennywise may have been based on the serial killer. While there is some debate on whether Gacy truly influenced the creation of Pennywise, the two are eerily similar, as both dress as clowns and target children.