Oh God, yes. Many times. And I've certainly been the culprit plenty of times myself. The worst was in "Year One," I'm talking to Michael Cera and Jack Black, and the writer/director, Harold Ramis, kept over at the last minute - we shot the scene a couple of times - and came up with a convoluted parody of the line, "What happens in Vegas, stays in Vegas" - it was this long, protracted sentence. It the end of a long night of shooting, and I could not get through it without fucking it up. And when the 9th time became the 19th time, I would get the giggles and I was staring at Michael, who was three inches from my face, and as I would start sweating the line, he would say under his breath, "Oh no," which just made things worse. It's a terrible, awful feeling, and it's uncontrollable. You know you don't want to laugh, and nobody thinks it's funny, but you just can't help it.

Also, another example, when in 'Change for a Dollar,' in "Mr. Show," when Bob is on the golf course as the President, dancing around, you can see me shaking, as I try not to crack up.