Oh, I'm sorry, Mig! I meant to reply to that!

Pennywise is the actual name of the clown in the movie/book, It. In fact, I just looked up the exact quote from the book, and he (the clown) says to a boy, "I, Georgie, am Mr. Bob Gray, also known as Pennywise the Dancing Clown." Not sure where Bob Gray comes from, but that's what he says.