After arguing with Kassie, Wally is seen walking in the rain. A truck passes behind him bearing an ad featuring a turkey baster. This is a reference to 'The Baster', the short story on which the film was based.
The film differs drastically from Jeffrey Eugenides' story "Baster" which features an unattractive man in love with a beautiful woman. The writer had nothing to do with the film, as he felt it was going "too Hollywood".
The trivia item below may give away important plot points.
Many people believe that neither Jason Bateman, nor Patrick Wilson, could be the kid's father, since he has brown eyes and they both have blue eyes; they think the father must have brown eyes. This is, in fact, not correct, as the genetics behind eye color are much more complex than dominant/recessive, and while it doesn't happen often, it is certainly possible for two blue-eyed people to have a brown-eyed child. This myth can be harmful, as it can cause unfounded doubt over the true identity of a child's father.