I was just perusing PLAYBILL.COM'S CUE & A: Will Swenson and one of the questions was this:
Worst onstage mishap: During previews for Lestat (yes, Lestat) we changed a scene to include the revelation of a crucifix around which the entire following scene would play out and reveal important vampire truths. Well, one night I forgot to bring on the crucifix. Nice job, Will. Douche.

Jose, did you see/hear about this?
I think I remember that.
I also remember getting the signal from the conductor to keep repeating a couple of measures. Over and over and over again. It turned out that the wigs on Lestat and Marius got caught "in each" other. I believe Marius' wig won. Of course since Lestat's mic was pinned into his wig, well...
And then we had that one performance where we wanted to try out a new opening - one of many opening sequences the show went through. We had spent the whole day of tech putting it together, and hoping that it would work. Since everything - lights, set, special effects, automation - had to happen at once and then in sequence, it was all coordinated with the "click-track" that the orchestra was playing with. We would hear a count-off of "1, 2, 3, 4" in our headphones, and then the conductor would bring us in. Well...
We get to the show that night, and we're all excited to see how the new opening looks. We hear the pre-show announcement in the house, the cue light goes off in the pit, and the conductor gives the downbeat. Then we hear "1, 2, 3, 4" in our headsets. SPOO!!!! I was up on the 7th floor with the other keyboard player - who was also the associate conductor - and when we saw the conductor start to give his prep, we just started waving our hands wildly hoping that he would see us. Needless to say, he didn't see us. So, we just kept playing. And started laughing.
A few measures into the brief overture/prologue, we could tell that the stage manager was blinking her light - signal for the conductor to pick up the phone. A couple more measures in, the flashing stops. We're still laughing and shaking our heads. That's when the conductor catches us in his monitor. He just smiles back at us thinking that we were trying to cause some trouble. Well...
A few measures later, we can tell that the conductor is hearing the click-track. And he notices that it is off by a measure. Ohhh...
After the prologue is done, the stage manager's light starts blinking again... The conductor picks up the phone, and, well... Ah, well.
And I don't think we ever ended up trying that particular version of the opening in front of an audience. Something new was tech'd the following day.