My new theory for the feet behind the curtain is that it’s meant to open to reveal a pair of disembodied legs that allude to the sawing in half trick (either being implied to be Larry’s or just another random characters). On the call board there’s a note from Houdelini asking for a new assistant for his trick, so maybe this calls forward to this? I lean towards this being a broken effect since the air blast seems out of place, and I think the legs peeking out is too subtile of a detail compared to where they hide small gags in the rest of the ride.