Guy walks into a restuarant. Waiter asks him for his order, the man says, coffree, no cream. The waiter goes, comes back and says...
"I'm sorry, we're out of cream. Would it be OK without milk instead?" Or at least that's pretty close... the point being that no matter what, the customer is still stuck with black coffee.
And the poster who said the scene is not about the joke is totally right... it's about poor melvyn Douglas trying everything to get Garbo to laugh and striking out... until he falls off his chair and looks like an idiot. Then she laughs.