Four days before filming, Corey Haim broke his leg and Dinger's character had to be rewritten to include the injury. While his actual cast was removed during filming, he had to wear a fake one for the remainder of the production. In the movie Dinger says that his mother hit him with her car. In real life, Haim broke his leg while trying to teach his mom how to ride a motorbike. She couldn't use the brakes well yet, and ran into the side of a building, breaking her nose and Corey's leg.
At the time of filming the two Coreys were both addicted to drugs such as cocaine, as well as Feldman using heroin at the time and having an obsession with Michael Jackson. He included Jackson style type moves in the dance sequence involving Lainie in the gym.
This was the last time Corey Haim appeared in a mainstream film. His drug addiction got him blacklisted from Hollywood, and he would spend the rest of his career making low-budget, direct-to-video movies. Though he did make a cameo in Crank: High Voltage (2009) alongside Jason Statham.
During a dream meeting between Bobby and Coleman, Bobby gives Coleman instructions to view Bobby's home movies to learn how to act like a more believable Bobby. When the film cuts to Coleman selecting a VHS tape of one of Bobby's birthdays, the audience can see a videotape on the shelf with Tora! Tora! Tora! (1970) marked on the label. Jason Robards, playing Coleman, also played General Walter C. Short in the 1970 WWII film.