- What Could Have Been: At the time of his death, he was working on his next project after Once Upon a Time in America called Leningrad: The 900 Days, which was going to be a film adaptation of the Harrison Salisbury non-fiction book The 900 Days: The Siege of Leningrad.
- Other unrealised projects include A Place Only Mary Knows, Don Quixote, Colt, a remake of Gone with the Wind that would have been closer to the book, a film adaptation of The Phantomnote (with the follow-up being a film adaptation of Mandrake The Magician) and a film adaptation of Journey to the End of the Night, which elements were used for The Good, the Bad and the Ugly and Duck, You Sucker!.
- He was an early choice to direct Flash Gordon. A fan of the original comic strips, Leone turned down the offer to direct as he felt the script didn't resemble the source material.
Trivia / Sergio Leone