Director Cameron Crowe couldn't find the love song he wanted until he heard Peter Gabriel's "In Your Eyes". Gabriel asked to see part of the movie, and Crowe had the production company send him an unfinished cut. Gabriel gave permission to use the song, saying he liked the film, but not the lead character overdosing at the end. Crowe realized that Gabriel had actually been sent a copy of Wired (1989).
The exchange between Lloyd and Jason about an album titled "Hey Soul Classics" is a reference to a TV commercial that aired frequently in the 1980s. "Hey Love" was a compilation of 1970s R&B songs that was sold on TV. A line from the commercial, "No, my brother. You've got to buy your own," became a catchphrase at the time.
Cameron Crowe commissioned The Smithereens to write the movie's theme song. They came up with "A Girl Like You." Crowe thought the lyrics were too leading (they outline the entire plot), so he rejected it in favor of Peter Gabriel's "In Your Eyes". "A Girl Like You" was included in their next album, "11", and in the movie Backdraft (1991).
Ione Skye has admitted on the film's audio commentary that there was definitely off-screen chemistry between her and John Cusack during filming, and that had they not been involved with other people at that time, they probably would have gone home together the day they shot the scene where Lloyd teaches Diane to drive a stick shift.
Cameron Crowe said in an interview, "Few people know this, but Stone Gossard is actually in Say Anything... (1989) He plays a cab driver, and Ione Skye looks at him and kind of flirts with him a little bit as they're stuck in traffic on her way to graduation."
Lloyd and Diane's school appears to be based on The Lakeside School, a very prestigious private school in Seattle. In the movie, the school is called Lakewood, and its mascot is a rooster, not a lion. In Lloyd's first phone conversation with Diane, John Cusack mentions that at his annual party, Lloyd "dresses up as the Lakeside rooster."
Lloyd makes several references in the movie to "Bell Square" mall, short for Bellevue Square (located in Bellevue, Washington). When Lloyd is driving in the rain and sees the mall, he is actually driving by Westlake Center (located in downtown Seattle).