Morgan tells Nick (Mel Gibson) that he "sounds like the guy from "Shine"." Geoffrey Rush, the actor in Shine (1996), was Mel Gibson's roommate in the 80s in Australia.
The scene towards the end in which Nick (Mel Gibson) visits Darcy (Helen Hunt) at her apartment is similar to a scene in As Good as It Gets (1997). In both movies Helen Hunt's character is at the top of the stairs and her love interest (Mel Gibson/Jack Nicholson) approaches her and says, "I had to see you."
In the bathroom scene, when Nick falls into the bathtub and nearly electrocutes himself, there's Swedish ad-poster on the wall. The text ("Härligt efter rakning") means "Wonderful after shaving".
The Nike representatives are in fact the real Nike ad representatives and not actresses.
The poem that Nick (Mel Gibson) starts reciting in order to keep from hearing his daughter's thoughts when he walk in on her and her boyfriend is "Casey At The Bat" written by Ernest Lawrence Thayer in 1888.
The ad agencies are loosely based around the Chicago agency Leo Burnett and the New York agency BBDO.
Mel Gibson's character works at Sloane Curtis Advertising, the same advertising agency Diane Keaton's character is fired from in Baby Boom (1987).
When Nick Marshall asks his assistants, Eve and Margo, if they know anything about Erin the file girl, Margo refers to her as "Mrs. Lonelyheart". This is an homage to the suicidal character in 'Alfred Hitchcock's film Rear Window (1954), made in 1954.
In the scene where Mel Gibson waxes his legs in his bathroom, he actually did wax his legs, and it did not hurt him nearly as much as it hurt him in the movie. He kept taunting all the women on set, saying "come on, this doesn't hurt at at all!"