I'm thinking the conversation about Casanova deserves a post of its own.
Various actors were considered for the title role- including Robert Redford, Marlon Brando and Al Pacino. FF himself favoured Gian Maria Volonte. When Volonte proved unavailable F settled on Donald Sutherland- whom he described in an interview as "a big, sperm-full waxwork with the eyes of a masturbator."
In the same interview, challenged about his hatred of Casanova, FF replied, "How could I have liked him after I had undertaken the task of reading the Memoirs? They are deadly dull, written with such fastidiousness that one never understands what he is talking about. They are just an ocean of paper, more tedious and depressing than a phone book...it's as if the Leaning Tower of Pisa had been rebuilt by convicts using toothpicks."
Maybe it's not altogether surprising that the film didn't work. Fellini himself accounted for the failure this way; "I wanted to destroy the myth of Casanova, I who had always maintained that myths were something vital, to be cultivated rather than destroyed. Now the myth was taking its revenge and destroying me."
All the quotes are from Fellini on Fellini, edited by Constanzo Constantini.