Mary Martin was once slammed into a wall when flying during PETER PAN.
At the Opening Night of NICE WORK IF YOU CAN GET IT, one of the female chorus member's heels broke causing her to fall. She performed the next number barefoot.
At a Six Flags theme park, I believe it was, there was a Looney Tunes show. Daffy Duck's costume glove fell off and Foghorn Leghorn had to try to help him put it back on. It's extremely difficult to grasp anything with these costume gloves, and they were having a difficult time. The glove fell onto the floor again, and was kicked onto dead center stage by Yosemite Sam. Porky Pig kicked it back upstage where a stagehand and Sylvester went backstage and was fixing the wardrobe malfunction. Now, if you can picture this, this incident occurred while the show's audio track played continuously, so all the characters had lines/lyrics throughout. I'm sure this confused all the kids when they could hear Daffy and Sylvestor talking, but their characters weren't onstage.
A few weeks ago at PORGY AND BESS, Norm Lewis exited the show at intermission and his understudy went on for Act 2. During the Storm, when he Porgy is supposed to trip and fall, his cane fell into the Orchestra Pit. An audience member in the front row reached in, grabbed it, and threw it onstage.
All three times I saw SPIDER-MAN, which were months apart, a bumblee fell off that ridiculous villain costume and almost tripped the next villain entering.
About 10? years ago at a performance of a national touring production of THE KING & I, a child climbed the steps onto the stage to join the other children.
I won't say which show, but last week I attended a performance where the lead actor had a snot bubble and as he shouted his next line, the snot shot out his nose and landed on his chest. And it was a HUGE glob! Luckily, it was his last line of the scene before exiting.
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle