The story about the man being killed by a gunshot while falling off a building has for years been used as a hypothetical case in criminal law classes to illustrate causation.
When Paul Thomas Anderson approached George C. Scott about playing the role of Earl Partridge, Scott threw the script across the room, saying "This is the worst fucking thing I've ever read. The language is terrible." Marlon Brando was also considered.
Claudia was the first character created, and the other characters were branched off from her.
Paul Thomas Anderson wrote the bulk of the script during two weeks he spent at William H. Macy's Vermont cabin - afraid to go outside because he'd seen a snake.
Aimee Mann's music inspired Paul Thomas Anderson to write the script and at least one lyric (and possibly more) from an Aimee Mann song was lifted and used as dialogue. In the song "Deathly" the lyric goes: "Now that I've met you / Would you object to / Never seeing / Each other again". In the film, Melora Walters's character says "Now that I've met you, would you object to never seeing me again?"
Paul Thomas Anderson: Anderson is seen immediately after the start of the show "What Do Kids Know?" confiscating from a member of the audience an "Exodus 8:2" sign.
Paul Thomas Anderson: [Iris In/Out] The very first story of the prologue is shot like a silent film. The first shot opens with the Iris In technique, used frequently during the silent film era to open and close shots.