I have to add my own, during "Cinderella" and thank goodness this was a final dress, my line goes - Everything is decided for me, what I do, where I go, who I see.  But it comes out - Everything is decided for me, Who I do, what I see, where I go. 

  This actually came out of my mouth during the final dress rehearsal for Arthur Miller's The Crucible.   I was playing Deputy Gouvenor Danforth and it was the dramatic last scene where I was to condemn John Proctor to death unless I could convince his wife to denounce herself as a witch.  The line which I was to growled loudly in my best classic delivery was "Woman has the devil dried up every tear of pity within you?"  However what came out was:  WOMAN HAS THE DEVIL DRIED UP EVERY PEER OF TITTY WITHIN YOU.  The laughter lasted for 20 minutes.  The embarrassment has lasted a lifetime.  This may be why I mostly directed now.

I love this topic!  Makes me feel a little better!  I was having kind of an off night about three shows into our eight show run of Fuddy Meers recently.  There is a moment in the show when another character throws a package of bacon onto the floor and I was supposed to angrily pick it up and put it back in the freezer.  Well, we had been using this particular package for awhile and it was a little.. damp.. from the bacon juices seeping out of the package (yuck!)  so when I grabbed it, the package flew out of my hands and went straight across the stage, barely missing one of the other actors onstage, and landing at the end of the stage, which was actually supposed to be another room of the house.  The line was "I'm sorry, I'll put the bacon back!" so after watching it fly across the room, I added "or not."  Luckily, my exit was not long after that incident!

Originally posted by biggertigger I am surprised that no one has mentioned the most famous of errors with body mics.  The dreaded sound people forgetting to shut off the mic while you are in the bathroom.  Of course you hear everything and the actor speaking so eloquently of the show.

Luckily this only happened in rehearsal...  We're doing "A Christmas Carol".  One of the scenes has Tiny Tim lying on the bed, dead.  Since the kid was such a trouper, it was actually him lying there, not a dummy.  But one night he sneezed!