My favorite spinal tap moment didn't come from the movie, but came from their live show a few years back when I saw them in st pete. Can't remember which song it was (pretty sure it was something from A Mighty Wind). They started the song, then stopped only a few seconds into it. Here was the exchange:
Harry Shearer: Wait, stop stop.
Michael Mckean: Is it over already?
Harry Shearer: Sorry, we played that way too slow.
Michael Mckean: If it's already over, I think we played it way too fast.
It took quite awhile for them to regain their composure before they started the song again.