Funny man Jack Black dressed up in a well-tailored tuxedo the other night and attended a black-tie gala in honor of pal Ben Stiller. The whole experience -- well, the suiting up part -- was both hysterical and humiliating, says the big guy.

First of all, Jack hates to dress up. "I was going to say screw it," he reports. "I was just going to wear my jockies and trench coat." But he followed suit after deciding he better look the part since he'd be sitting next to the sharp-dressing Robert DeNiro and P. Diddy. So, off to Bergdorf Goodman he went, where he was greeted with this comment from the sales lady: "Your neck ... it's too big. It's too big for this store! I'm sorry Jack Black, but you might want to go to Big and Tall."

Ouch. Black became flushed with shame and marched off to, yes, the Big and Tall store. "I was welcomed with loving open arms by my people," Black reports. No mention of any plans for trimming down. Perhaps the star is happy with the skin he's in.