Shortly after the film's release, Huey Lewis sued Ray Parker Jr. for plagiarism, alleging that Parker had copied the melody (primarily the bassline) from Lewis's 1983 song "I Want a New Drug". The case was settled out of court in 1985 for an undisclosed sum and a confidentiality agreement that prohibited discussion of the case. According to Parker, there were several lawsuits at the time, because "when you sell that many records, I think everybody wants to say that they wrote the song." Parker later sued Lewis for breaching the confidentiality agreement in a 2001 episode of VH1's Behind the Music by reasserting that Parker stole the song. Regarding his case against Lewis, Parker said, "I got a lot of money out of that." Lewis said it was at least $30,000 in an interview with Dutch television NPO.
In a 2004 article for Premiere magazine, the filmmakers admitted to using the song "I Want a New Drug" as temporary background music in many scenes. They also noted that they had offered to hire Huey Lewis and the News to write the main theme but the band had declined. The filmmakers then gave film footage, with Lewis's song in the background, to Parker to aid him in writing the theme song.