In the original script Manglehorn was a criminal who had gone straight. He met with his old partner who was hiding out in a senior citizen's home and his mysterious back story was explained. There was also a massacre at Dawn's bank and a massive earthquake that brought forth Clara. This was all edited out of the final film.
After co-starring in this film, Harmony Korine cast Al Pacino to star in his next feature, The Trap
The film cast includes two Oscar winners: Al Pacino and Holly Hunter. In fact, Hunter was given the award by Pacino himself, the Best Actor winner on the previous edition of the event.
Pacino greatly appreciated getting to know Harmony Korine while making Manglehorn; Pacino said, "Harmony was mesmerizing. We have a scene together that takes place in a spot that's sort of a cross between a casino and a penny arcade. Harmony started improvising as his character in the film-he went for ten minutes and was out of this world. I was just playing my role, wondering where he was going to land. I felt I was actually listening to James Joyce or watching Robin Williams. I could not believe how this man spouted. I know that footage must be somewhere, but just like the original ending we shot, it didn't end up in the movie either."
Al Pacino said the best thing about making Manglehorn was having dinner with Terrence Malick (in Austin, Texas).