The film was inspired by an article in 'Time' magazine about David Phillips, a University of California civil engineer who stumbled upon a lucrative frequent-flyer promotion. By purchasing 12,150 cups of Healthy Choice pudding for just $3,000, he accumulated 1.25 million air-miles.
In a scene in the hotel in Hawaii, Lena is asked to unload the "484's." In another of Paul Thomas Anderson's films, Boogie Nights (1997), Buck's boss at the stereo shop tells him to unload the "484s."
At one point in the film, Adam Sandler (Barry) is being followed by the Steadicam as he talks on the phone. During one take, the front of the camera accidentally bumped into a table and knocked the camera briefly, causing the shot to jump from Sandler to an image of an out-of-focus piece of the set and then quickly re-adjust. Paul Thomas Anderson loved the effect and wanted to do it again, so the crew did more takes and right at the same point in the dialog, they smacked the front of the matte box on the camera to re-create the look.
The four blond brothers who go after Barry and beat him up are actually brothers in real life.
The song "He Needs Me", the theme of the movie, is from the 1980s movie Popeye (1980) with Robin Williams and Shelley Duvall, who sang the song. It was written by Harry Nilsson. Composer Jon Brion wrote score over top of the original and renamed the song "He Really Needs Me," which is the version heard in the film, although both are included on the soundtrack.
'Sean Penn' was originally going to play Dean Trumbell but had to drop out.
John C. Reilly was originally supposed to play one of the men who come from Utah to collect the money. But Reilly thought that it was a strange role for him, considering how everyone would recognize him and would wonder why he was not doing more. So he dropped out.
Director Trademark: [Paul Thomas Anderson] [iris in/out] After Barry and Lena have gotten together in Hawaii, there is a shot of them walking down a hallway, away from the camera. They hold hands, and the shot closes with an Iris Out, the circle going around their hands.
During the scene where Barry is at the supermarket looking for the cheapest Healthy Choice food item, he is being followed by an out-of-focus character in a red outfit. It's Emily Watson's character, before they've been introduced.
When Barry says, "That's very food," it was actually just a typo that the director decided to keep.
The film has no opening titles. All titles and credits appear at the end.
The address listed to return the frequent flyer promotional coupon is Healthy Choice Frequent Flyer Offer, P.O. Box 440201 Dept A, El Paso, TX 88544-0201. This is almost exactly the listing from the original promotion, except the second line read "Dept. E" instead of A.
Barry gives a Master Card number to the sex line. Master Cards begin with the number "5" (Visa is "4," AmEx "3").
When Barry punches his office wall then rests a bloody hand on his piano, the cuts on his knuckles spell the word 'love'.
In the goofs section, a mistake is noted on the hotel. The hotel is advertised as the Sheraton, and bathrobe is adorned with a Mandarin emblem. The hotel is actually the Princeville and was intentionally confused. One of the Princeville's motto's: "Perfect for Romance".