When I was doing the original LA company of LES MISERABLES at the Shubert Theater in Century City, in the opening sequence I was a prison guard watching over the chain gang, and I was supposed to drink from a prop wooden canteen.
One performance I held it up to my mouth to "take a drink" and the old prop completely crumbled in my hand and went all over the turntable floor. It was hilarious and we had to scramble to get it all up before the scene was over so it would not get caught in the tracks on the deck, but try to do it discreetly so as to not detract from Javert's entrance and the plot occurring onstage.
Another time I was doing the role of Thenardier, The Master of the House with Kay Cole, and 2 things happened almost at the same time: my mic went out mid line AND I blinked and my contact lens flew out of my eye. They replaced my mic for the next entrance, but my lens was never to be found (a grey lens against a grey deck....forget it, gone!) Was going through the rest of the show with clear vision only on one side. Eeesh!
And of course the first time going on as Molina in the original company of KISS OF THE SPIDER WOMAN opposite Chita Rivera: at the end of show I do a big tango dance with her. And while it was happening, I was thinking "Oh my gosh, I'm actually dancing with and kissing Chita Rivera!--Anita, Rosie, Velma etc., etc. This is crazy and amazing!"