I'm 2nd AD on a TV show currently in production and I heard something over the walkies on set that made me laugh out loud (good thing we weren't shooting)!
Kind of like the trumpet player and conductor conversation:
Trumpet player missed his first few notes
Conductor: Mr. First Trumpet, do you know where we are? (in the music...)
Trumpet player: No sir, I'm as lost as you!
Sorry -- no... now that I think of it, it's not anything like that. Ugh... even have to explain the joke.
One I heard on set between Director & DP (wont use the real names)
Director: Morning Gus.
DP: Morning . . . ready to shoot crap . . .
Director: What?
DP: I was figuring shooting beautiful stuff isnt getting us noticed . . . the real deal is to shoot crap, right
Director: Err . . . ok . . .
DP: great . . . guys this morning were gonna all shoot some crap!
Master Electrician: (something) was up all night.
Stage Manager: All nighter?
M.E.: Yeah, Comparative Lit paper.
Stage Manager: Sucks. I've never had an all-nighter, but I've had a lot of blow offers.
(At which point the entire theatre, most of whom were on headset or could hear in the greenroom and backstage, fell dead silent and then busted a gut.)