The Fender Stratocaster guitar used by Michael Paré as Eddie Wilson in the concert scenes formerly belonged to John Lyon, a technical consultant for the film. Lyon is better known as Southside Johnny, leader of the New Jersey shore band the Asbury Jukes, and longtime friend and frequent collaborator of Bruce Springsteen.
In the scene where Frank (Tom Berenger) is watching Sal (Matthew Laurence) at the nightclub, Sal's band is playing "Betty Lou". Sal takes his hand off of his bass guitar and even slaps it but we still hear bass lines being played.
Eddie Wilson: [to the audience, a few days after Wendell Newton's death]
The other day, I buried one of my best friends. He was the best sax player I ever heard. And they tell me I gotta come up here and entertain you people now. I don't think I'll be able to do that.
Helen Schneider (who played Joann Carlino) left the film industry in the early eighties, after she moved to Germany. She went on to have an illustrious career there, becoming a best selling jazz and pop artist, appearing in many big budget stage productions and making several appearences on German television. She is still quite big in Germany to this day.