Undercover student

During production, Judd Nelson decided to go undercover at a local high school outside of Chicago.

There, the actor convinced his peers he was a legitimate student, and bought them beer with his "fake ID" - Judd was 24 years old at the time.

Looking back at the situation, the actor revealed how he kept his peers’ suspicions at bay.

He said: "They would ask me why I was staying there, and I told them my dad was in jail. I'm staying at the Westin O'Hare while my dad's incarcerated."

The movie was actually shot from March 1984 at Maine North High School in Des Plaines, Illinois, which had been closed in May 1981.