I don't know if you're familiar with the now-defunct HBO show 'Extras,' but if you haven't seen it, you should. It stars Ricky Gervais, the demented brain behind The Office (UK), and features various actors playing themselves, sort of asshole/idiot versions of themselves behind the scenes on fictitious film shoots.
Anyway, this clip is from the extras of 'Extras,' and it came along at a great time. The play we just opened last night (And the Winner Is...) is really funny on its own, but with the goofy, hilarious shite my fellow actors have been doing on stage, I was cracking up right up until wednesday and thursday night of tech week. This clip talks about cracking up inappropriately on set ('corpsing,' in Brit argot) and has clips of Ian MacKellan, Daniel Radcliffe et al, dying horribly in gales of laughter.
check out the show, some bits here.
OH!!! and i almost forgot about this one with clive owen. so cruel, so funny. :)
and my fave of all time: Ian McKellan. "how do i act so well?"