A subplot of 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.
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 readjust. 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 dialogue, they smacked the front of the matte box on the camera to reproduce the effect.
John C. Reilly was originally 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 people would recognize him and wonder why he was not doing more. So he dropped out.
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.
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. A" instead of E.
Unusually, Jon Brion composed music for the film while filming was taking place, experimenting with tones and sounds, making particular note of what director Paul Thomas Anderson was responding to. Brion's score would then be played on set, helping to influence the tone of the film.
Paul Thomas Anderson first announced that his follow-up to Magnolia would be an Adam Sandler comedy at a press conference at the Cannes Film Festival. The news was greeted with laughter by the assembled press. When "Punch-Drunk Love" eventually played at Cannes, Anderson won the Best Director Palm d'Or.
Anderson deliberately wanted to make a very different film after the rigors of making Magnolia. He felt he had reached a dead end with his previous multi-character movies and he also wanted to subvert the critics' expectations of his films. Being a close friend of Adam Sandler, it seemed like a natural fit to make a project with him.
When Barry begins to tell Lance about the extortion scheme he has become a victim of, at one point Adam Sandler suddenly stares at the pudding on his desk. Just before he looks, an electronic voice on the film's sound-track faintly says, "Come here, Barry."
When Barry says, "Business is very food," it was actually only a typo that the director decided to keep. In the movie Popeye there's a song called 'Everything is Food' (though not included on the sound-track album) by Harry Nilsson. The song 'He Needs Me', by Harry Nilsson, which is featured prominently in 'Punch-Drunk Love', is originally from the Popeye sound-track. This is a strange coincidence because while Barry used the word "food" in place of "good" as an accidental slip of the tongue which originated from an error in the script, in Popeye the word "food" was used in place of "good" as an intended play on words.
Reversing an audio recording of the name "Lena" yields "añil", a plant source for indigo dye. For most of the film, Barry is shown wearing his strikingly indigo-colored jacket. Together, her name and his color form an aural symmetry.
Paul Thomas Anderson:
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.