When Elaine brings Duff the basket of cheese, there's some discussion of the origin of Gruyere cheese. Duff is correct. Gruyere is from the Gruyeres district in Switzerland, not from France.
Nick Offerman, Megan Mullally's actual husband, is one of the electricians that sneak out of Patty's bedroom.
Even though the movie is set and filmed in the US, a few distinctly Canadian items do appear in the movie, such as cases of Moosehead beer and a Canada 3000 handbag.
In the dial a bottle scene where Duff wads the flyer up and throws it back in the car it hits the girl in the face and her reaction is genuine.