The street that the St. Elmo bar is on is in the Universal back lot. Two or three buildings to the left is the Hill Valley Clock Tower from Back to the Future (1985).
Much like her character, Demi Moore (Jules) had a drug problem when she was cast in the film. One day, director Joel Schumacher actually demanded that she leave the set because she was really high. Moore had to go through rehab and promise to stay clean in order to play a character with a drug problem. Moore revealed in an auto-biography later that she had a cocaine problem and was using an eighth of an ounce of the drug every two days. She went to treatment for 15 days and then had a counselor with her while shooting the film.
The "booga-booga" cheer that the friends do when they are celebrating or just in a good mood was not originally in the script. In a later interview, Rob Lowe (Billy Hicks) stated that the cheer came out of observing fans whispering about the stars of the movie and then laughing. The cheer itself makes fun of what these whispered conversations sounded like from a few feet away.
Emilio Estevez (Kirby Keger) and Demi Moore (Jules) began dating during the filming of the movie. He said he was "deeply in love with her." For a time they were even engaged, though they never married.
According to director Joel Schumacher, he had to fight hard to cast Demi Moore (Jules), Judd Nelson (Alec Newbary), Emilio Estevez (Kirby Keger), Andrew McCarthy (Kevin Dolenz) and Andie MacDowell (Dale Biberman). Schumacher says the studio had easily approved Rob Lowe (Billy Hicks) (who was a teen idol at the time), Ally Sheedy (Leslie Hunter) (who had been in the hit movie WarGames (1983)) and Mare Winningham (Wendy Beamish) (who had a significant body of work in television).
Patrick Winningham: The brother of lead cast member Mare Winningham (Wendy Beamish) as a band member of 'The New Breed' Band.