It Chapter 2: 15 Insane Hidden Details You Definitely Missed
4. Mrs Kersch's Chest
Bev should really have noticed something was off with Mrs Kersch from the moment she opened the door. There was, after all, a huge hint in the fact that the voice that greets her isn't that of Joan Gregson who plays her, but is in fact Bill Skarsgard's own voice.
From there, things get gradually more and more weird, until she eventually goes full Baba Yaga and attacks Bev, who has by then twigged that she's Pennywise in disguise.
Before that point, though, It gave her an even bigger hint by flashing Mrs Kersch's chest for a moment to reveal what looks like a clump of blisters. So why's it a tell? Well, back in the original, Mike stabs Pennywise with a fence post in the chest, almost killing him - obviously some scars are lasting even for the clown.