Corrected entry: In the party scene where all the couples put their keys in the pot at the begining, there are equal numbers of men and women. However, Kevin Kline ends up in a drunken stupor in the bathroom, and yet at the end there is only one woman left with one man. What happened to the extra woman?
Corrected entry: When Paul goes to get the beers out of the fridge in Libitz's house, he opens the fridge door and takes out two beers. Then he clearly slams the fridge door. A second later, we see him walking back into the living room and he is carrying not two, but three bottles of beer.
Correction: If you look carefully, he grabs the third with his thumb in the same hand then slams the door with his other hand.
Correction: Remember that one of the guests brings his bachlor son to the party (who incidently ends up with Sigourney Weaver's character). This would account for there being two men left for one woman.