In an effort for Tom Cruise (who was 20 during filming) to look more "teenage" in appearance, the producers put him though an unusual bit of physical training. Cruise worked out seven days a week, in order to lose ten pounds. Once that had been accomplished, he immediately ceased working out and ate extremely fatty foods in order to add a layer of baby fat. This is how he achieved that "fresh-faced" teenage look.
Curtis Armstrong, making his film debut, kept a journal during filming. On his early impression of Tom Cruise he wrote: "Tom's an interesting character. Can't really make him out. He would appear to be on the brink of a great career. But when it comes to doing things with him - socially or professionally - he's not terribly reliable. Always late, very casual with other people's time. But in spite of it all, it's difficult not to like him. Though it's early days, the rehearsing I've done with him has gone smoothly. No arrogance or selfishness there. Yet. We'll see."
The sunglasses Joel wears are the Ray-Ban Wayfarer model. Annual sales of Wayfarers were languishing as of 1983 but skyrocketed 2,000 percent after the movie's release. This film and The Blues Brothers (1980) have contributed to the popularity of the Wayfarers since.
According to Tom Cruise, Paul Brickman was initially unsure of casting him: "Originally, Paul had seen Taps (1981) and said, 'This guy for Joel? This guy is a killer! Let him do Amityville III!' Somehow, my agent, without me knowing, arranged to have me just drop by the office to say hello. So I went in wearing a jean jacket, my tooth was chipped, my hair was greasy. I was pumped up and talking in an Oklahoma accent, 'Hey, how y'all doing?' Paul just sat there, looking at me." Cruise returned to Tulsa to finish filming The Outsiders (1983), but flew back to L.A. and auditioned again. "I walk in and see this stunningly gorgeous woman sitting there looking at me and I'm thinking, 'Oh my God,'" Cruise said. "Rebecca [De Mornay] had already been cast. They wanted to see the two of us together. I tested, and to make a short story long, we didn't test that well. Paul just believed in me."
The dance scene where Joel dances to "Old Time Rock N' Roll" was completely improvised. In the script Tom Cruise was simply instructed to "dance to rock music."
Sean Penn: as the man sitting in the passenger seat as Joel first takes the Porsche for a spin. The cameo was a favor for director Paul Brickman.