Well, the show op'ned. Oh yes it did.
So did the fire alarm system. Twice.
In spite of all best intentions and a week of rehearsals in which all went swimmingly (see what I did there?), the fog machines set off the alarms which had supposedly been turned off in the auditorium (with fire marshall's approval). The audience was told to stay where the hell they were, and about twenty minutes later the show resumed.
When it went off again later, we played, sang, and acted right over it, and they got it shut off within a couple of minutes.
The upshot is that they're going to have to shut it down for the whole school because the fog can travel.