There was a time when it was a hole in the popcorn bucket

I think he meant a different type of clapping involving very different body parts...

yes but it implies that clapping after a movie is normal and acceptable which it is very much so not and only servers to annoy everyone else involved

Eh, where I live, especially with a full audience, you get claps if it's a dope movie with an amazing ending. Now... something like Infinity War didn't, but... for obvious reasons.