The worst flub experience I ever saw on stage was when I was playing Noah in THE RAINMAKER in St. Petersburg, Florida. James Drury was playing Starbuck. And Larry Drake was playing Jimmy (as an over-eager puppy by way of Hoss Cartwright). Our H.C., who was not a sterling actor to begn with, I think had been soaking up too much Florida sun and mai-tais around the pool in the afternoon and started playing the role like he was on vacation. One night in the opening breakfast scene, he skipped a whole page of necessary expository dialogue between him and Lizzie, who was played by a wonderful actress Deanna Dunagan. Since it was a scene between her and H.C., there was absolutely nothing Larry or I could do to help bail her out and we could only look sheepishly at each other over our coffee cups at the breakfast table. In some sort of magnificent tour de force, Deanna manage go back and seamlessly pick up all the lost dialogue and bring H.C. right back to where he'd screwed up the first time and he still couldn't get out the right line, leaving Deanna to say it for him, "And, pop, I know you were going to tell me you think I'm beautiful anyway, but..."
Boy, when we got off stage, Larry was in a towering rage and lit into H.C., decimating him with the ultimate insult, "You know, you USED TO BE GOOD in this role." Which was actually a lie, because he had never been more than adequate in the role. But it certainly cowed him.
I can only remember a few times where I've fluffed lines. I've never had an incident where I actually missed pages of dialogue or an entrance or anything. Or went up, dead cold.
Cyd Charisse was rather amazing to work with, because she was great out bailing people out when they went up...unless they weren't standing where they were supposed to be. Being a dancer, she was related to everything by movement. So if the blocking got off, she was thrown.
Martha Raye used to have planned break-ups in her shows. They were actually quite a challenge as an actor to try and make them as credible and spontaneous as possible. There is nothing worse than fake, forced, phoney laughter.
I used to have a friend in MacBeth who would always try to crack me up when I was playing Malcolm. I had the final speech upstage with everyone having their backs to the audience. One night this actor, Tim, pulled out from his tartan...unseen by the audience but quite visible to me...a good luck token from his dressing room -- A Sesame Street Grover puppet. I almost went up that night with this stupid puppet peeking out from under this guy's tartan.
Later Grover got kidnapped (not by me) and ransom notes would appear in different places on stage where Tim could find them. I think the puppet would also make sudden appearances on stage where Tim could see him, but couldn't get to him. One night Tim finally opened up a piano in The Imaginary Invalid and there was Grover lying on the keys.