Many actors and singers turned down roles in the film, including Olivia Newton-John (Strawberry Fields), Donna Summer (Lucy), Elton John, Barry Manilow, Bob Hope (Mr. Kite), Doris Day (Mrs. Fields) and Rock Hudson (Mr. Fields).
Alice Cooper checked himself into a New York rehab facility (which he quickly discovered was more of a mental asylum) for alcoholism. He was granted a temporary leave for three days (November 18-20, 1977) to record his vocals and shoot his scenes for the film.
No, none of The Beatles were involved in the production, other than being given songwriting credit. However, George Martin, The Beatles producer, did produce and arrange the music for the movie. It has long been rumored that Paul and Linda McCartney and George Harrison appear in the celebrity line up at the finale, but this is not true.