Every Hidden Pennywise From IT Chapter 1 & 2
3. The Funfair Clowns - It Chapter Two
After Bill meets Dean (the kid who WAS a fan of Richie until he met him and basically just screamed in his face), he realises that Pennywise is targeting him as a means to punish Bill more. After all, he lives in Bill's old house and Bill is haunted by not being there for Georgie when he needed him: what better way to open his wounds than by making him relive that again?
Bill's realisation leads him to the funfair where he sees Dean enter the fun house through the mouth of a clown. Massive warning alarms going off all over the place at this point. Eventually they both end up in a hall of mirrors that ends up being more like a rat's maze, but before that Bill has to navigate a room of swinging clowns.
Not just any clowns either. Half of the room's swinging monstrosities are dressed the same as Tim Curry's Pennywise from the 1990 adaptation.