While "visiting" 1960, Peggy Sue warns her sister about eating red M&Ms. Red M&Ms were discontinued in 1976, when Red #2 dye was named as a suspected carcinogen. In 1986--after the film was released--red M&Ms were reintroduced with a different red dye.
In the original script, Rosalie, the woman in the wheelchair at Peggy Sue's high school reunion, was a gymnast who was crippled in an accident. In the original script, Peggy Sue tried to take advantage of her knowledge of the future. She invented pantyhose, encouraged people to invest in Xerox, and tried to prevent Rosalie from hurting herself.
When Debra Winger was attached to star, she asked Penny Marshall to direct the film. Marshall met with Tom Hanks and Sean Penn for the male lead, but was fired three weeks into pre-production by the producers, who felt that the film had gotten too big for a first-time director.
Kathleen Turner usually feels the role she's playing intensely. In this movie she had terrible nightmares about her dead grandmother calling her on the phone, similar to what Peggy Sue feels in the phone scene.
The opening shot of the film is an optical illusion. Because the camera and crew would have been seen in the reflection of the mirror had the scene been shot in a conventional manner, there is a body double for Kathleen Turner (only she can be seen from behind in the shot) on the other side of the "mirror", doing the exact opposite of the star's movements, giving the illusion that Turner and Helen Hunt are reflections, when in fact they are the real actors in tableau with a body double sitting in front of them with her back to the camera in front of an empty mirror frame, framing a hole in the wall of the set.
Throughout the film, the phrase "Why, I oughta . . . " always brings immediate laughter from everyone. The was originally a catchphrase of Moe Howard's character from his shorts with The Three Stooges.
Charlie (Nicolas Cage) begs Peggy to marry him, saying he doesn't know what the future might bring; he might lose his arm, even. In Cage's next film, Moonstruck (1987), he played a baker who has lost his hand.
When Peggy Sue leaves the school's nurse's office and is walking down the hallway with Maddie and Carol, she sees a mylar balloon floating near the ceiling. The balloon was one of the decorations at the 25th-year class reunion that Peggy was attending when she suddenly fainted.