(at around 30 mins) At one point in the movie, Bobby is meeting Sandra's mother Mary Duvan, and says playfully: "How is it you are Sandy's mother and not her sister." In real life, it was Bobby Darin himself who discovered that the woman he thought was his older sister was actually his biological mother.
The Writers Guild of America, after sorting through the mess of writes, rewrites, and re-rewrites, decided that the screenplay is credited to Kevin Spacey and Lewis Colick who worked on it back in 1987 when Warner Bros. hired him.
During the song "Some of These Days", Kevin Spacey says "ah, do it, Sophie", as Bobby Darin did in the original recording. This is a reference to Sophie Tucker, the "Last of the Red Hot Mamas", who first recorded the song on February 24, 1911, and later re-recorded it in 1926.