Kevin Spacey as Bobby Darin. Spacey also directed and gets a writing credit. Darin seems to be an obsession of his.
The most amazing, utterly incredible thing about this movie is that Spacey is one helluva pop singer and dancer. Ebert said he was better than Darin (then he took it back but still…). If you like Spacey, you’ll want to see this movie.
Otherwise, not a great film. The concept of your boy-self as a guide for exploring your adult life just doesn’t play that well and frankly, it’s not that interesting. (We just watched De-Lovely, the Cole Porter biopic with Kevin Kline, and they employ what seems an angel as a guide for Cole to explore his path.)
I did not know that Darin wrote and performed Splish Splash, a throw-away song about taking a bath that became a teen hit. That song got him on American Bandstand and branded him a pop and rock singer in the very early days of rock-and-roll. He didn’t like that. He wanted to be a crooner like Sinatra.
Darin also performed Mack the Knife which is a great Bertold Brecht/Kurt Weill song.
Check the IMDB trivia section for some interesting stuff (rumors? facts?). Supposedly Tom Cruise (and several other hot male properties) were offered the Darin part.