I confess that I was once a late comer! I was late to The Magic Flute because we couldn't find parking.

And because I was sick and couldn't unwrap my cough drops before the opera started, I had to do it during the opera. I still feel terribly about it.
I definitely can't compare with some of these stories, but...
When I saw the RENT tour, these RENT heads in the front row were singing along, standing up and dancing. In general, the audience was so loud, it was hard to hear the lyrics and whatnot. It's great that they're enthusiastic, but this isn't a concert...
When I saw All Shook Up, everyone was singing along. So annoying.
But the one that takes the cake for my experience is when I saw Othello with my school. The people from my school behaved fantastically. But there were people from other schools who were just terrible. In Act VI when Desdemona was in her nightgown, they catcalled, hooted, and hollered. You know, right before Othello's heartwrenching monologue and her murder.
Jimmy, what are you doing here in the middle of the night? It's almost 9 PM!