The makers of the movie Ghostbusters (1984) originally asked Huey Lewis to do the soundtrack/theme song. He declined. So they got Ray Parker Jr. to do it... and after it was released, Huey Lewis sued Parker for plagiarism because it sounded so much like his 1983 song "I Want a New Drug".
Years later in 2004, the filmmakers admitted to having used Lewis' song "I Want a New Drug" as temporary background music and included those scenes in what they sent to Parker to help him write the theme song.