Pennywise the clown smurfed me up from a young age.
The part where the kids are looking through the old book and it turns into a black and white video. You see him come cartwheeling into view. Then he suddenly stops, looks up at the camera, points at it (at you!) and makes this horrible, horrible growl. Then he comes running, climbs up the lamp post and his FREAKY SMURFING FACE IS RIGHT THERE!!
Attachment 64601
I didn't sleep for a long time after seeing that...