In a general live performance sense, this is fairly common, for obvious reasons. Just a few of the things that can invoke it:
You're the singer, and you've just forgot your lines or you've came in at the wrong place or you've fallen to Vocal Range Exceeded. Or, alternately, you're one of the other members of the band and you notice the singer is in trouble. Similar for guitarists making major errors (or having lied about their skill level beforehand), and really a problem if the drummer or rhythm guitarist is the person having issues keeping the beat - that often induces a small version of Mass "Oh, Crap!" with all the other band members realizing just how bad the song's going to sound and how bad the gig is likely going to be.
Someone has gotten sick or injured onstage or in the audience. This one easily turns into Mass "Oh, Crap!" as well, for obvious reasons.
One of the band members' sound output is failing somehow. Worst is if it's one of the guitars (including the bassist), or the keyboardist, because that carries the possibility that the instrument itself failed (though it's usually only a loose connection) - and while most venues do carry extra mics for a singer to use in a pinch (or can patch him/her directly into the PA system with a lapel mic or a smartphone if set up for it and all else fails, though this is often avoided because it will make the singer much louder than the band), most don't have a stray electric guitar or bass or keys lying around, and even if the person has a backup, the show has to stop to set up his/her gear again for the new instrument.
"But you could have heard a pin drop - when Johnny stopped and locked the door..." 
In "Dinosaurchestra Part 3" by Lemon Demon, the time machine which the narrator used to go back to the late Cretaceous period and start a rock band with dinosaurs can't make the return trip, and then..."What's that rock way up in the sky?"
In the Gorillaz video for "Stylo", when 2-D and Murdoc realize that they are being chased and shot at by none other than Bruce Willis.
In the beginning of "Welcome to the Jungle," a singer briefly and subtly says "Oh my...god" before any of the intro gets through.
In the song "Get My Gun" by D12, Eminem angrily threatens a fan with a gun:
The narrator in "One" by Music/Metalica has this when he realizes that he lost his sight, speech, hearing, and limbs due to a landmine, but his mind functions perfectly so he is a prisoner inside his own body.
In the Ice-T song "Midnight" Ice-T, Evil-E, D, and Hen had just stopped two people from carjacking them. Ice then turns to see that the jackers had brought along a bunch of their friends.
Looked to my left, There were two more carloads, Niggas in hats and hoods, In an attack mode, And they hadn't yet begun to fight