Not Broadway - but during the Pre-Broadway run in Chicago, the Tomb in Aida (which originally "floated" in mid air)collapsed during the final scene. It sent Adam Pascal and Heather Headley crashing to the floor. The show was stopped and the Stage Manager literally asked the audience if there was "A Doctor in the House."
Don't forget Idina Menzels fall in Wicked, and the actor's fall from the ship in Little Mermaid.
Also, the set for Sunset Blvd was notorious for moving on it's own (well, due to cell phone "waves") and occasionally tripped up actors.
I once saw "Bertha" the Elephant fall when it was taking the stage in the parade at the start of Lion King. The entire thing went over taking down all four "legs." They got back up, and the audience cheered, but it was obvious once one leg goes - they all go.
Updated On: 12/12/12 at 11:37 AM