Pennywise is played by Tim Curry [from The Rocky Horror Picture Show, Legend, Addams Family Reunion, Clue, Hunt For Red October, Earth 2, Dinosaurs, Duckman, Mighty Max, Captain Planet, Tale Spin, Pirates of Dark Water, Gargoyles, Freakazoid and Darkwing Duck].
The actual creature can take any form, but mostly appears as Pennywise the Clown. He works a little like Freddy Krueger in that he customizes his terror to his victim. Appearing as Bill's dead brother, Beverly's father, etc. You can explore the rest of InfiniteCoolness.com using the links at the top of the page, and if you're looking for a picture that's not here, try posting a request on the board. Thanks for stopping by!