- Groundhog Day, first preview: Many people know the story, but immediately following the opening number of the show's first preview (filled with an entire comped audience of fans), one of the 4 turntables broke. They paused the show, and after an hour, the director and Andy Karl came out and announced they'd do a concert version of the show, which was just magical. They did all of the lighting cues which was a bit distracting as the cast just sat on any set piece that resembled a seat, but it was so special. When the snow fell during "Seeing You", the audience erupted and it's one of the view times my cynical a$$ has cried during a show.
- Rocky, mid-previews - During the second week of previews, the creative team rewrote much of the show and we were seeing the first performance of the new material and staging. The set broke 3 times in act one, resulting in multiple 30 minute holds. The show did run overtime I believe, ending a bit after 11pm.
- American Psycho, final week - It was fleet week, and during "Killing Spree," Ben Walker opened the song with "Hey pretty sailor," referring to the sailors that occupied the front row, instead of "Hey pretty girl". Unfortunately, the audience laughed so hard, Ben lost his place in the song. This was a huge mistake, because the song was 100% digital and tracked, thus the orchestra/conductor/music director could not loop the section back he missed. The sequence is 5 minutes and highly choreographed with many specific moments, and Ben missed all of them. He asked the SM to stop the show via the mic he held during the song, but they kept going. It was wild and if it had been my first time I would've been so confused. That was the best scene of the show, and is on YouTube if you haven't seen it.
I'm sure there's more, but those are the ones I remember most vividly.