Marc B. Wrote:Brando was, I believe, the main reason where this fiasco begins. Superman did extremely well at the box office so Brando demanded he get a bigger paycheck for his footage in Part II even though all his material had been shot. The studio refused and told Donner to re-write Brando's stuff and re-shoot it. Donner refused and requested they just pay Brando.
I'm not sure how much Brando had to do with the Donner fiasco. There was definitely controversy over Brando, but the Salkinds (producers) didn't get along with Donner pretty much from the beginning. Richard Lester was actually hired as a liaison between the producers and Donner during filming to minimize their contact with one another. It was that bad. (One might argue that the producers were grooming Lester to replace Donner, too.)
One of the most publicized conflicts between Donner and the Salkinds involved the tone of the film. The latter wanted a more comic and campy feel, something they got when they replaced Donner with Lester. That's one of the main things fans commonly disliked about Superman II.
Marc B. Wrote:The studio decided to just fire Donner and brought on Richard Lester to complete Superman II. Lester used some of the material Donner had shot but decided he wanted to go a different route so much of what we have known as Superman II includes new material shot by Lester.
It was more than just a decision by Lester. At least 51% of the footage had to be shot by Lester in order for him to be credited as director. Since, as you said, roughly 3/4 of the movie was already done by Donner, some of the footage was reshot by Lester in order to deny Donner his director's credit. This was almost certainly motivated by the Salkinds' dislike of Donner and wasn't really due to Lester. Lester seems more to have been caught in the middle. Donner did resent that Lester didn't contact him and let him know what was going on, though, since they were good friends on the set. He was still waiting for the word to go back and finish shooting on II when he was up and fired.
Lester's version of II featured maybe 30% Donner footage. Everything with Gene Hackman, for example, was shot with Donner since Hackman refused to come back and shoot anything else after the way Donner was treated (everybody pretty much loved him except the producers, from what I've read). You can tell Lester got a really bad voice double for Hackman in a couple of scenes if you're paying attention.
Margot Kidder was very public in her condemnation of the Salkinds and their treatment of Donner, too. In response, she was almost entirely written out of Superman III (though she may be grateful in hindsight).
Blake