Got a DEFCON-1 level backlash from EON, who became hell-bent on preventing any other Bond production not authorized by them from taking place, setting the stage for their feud with Kevin McClory later.
Also got one from star Peter Sellers, who wanted a serious Bond film but wound up with another comedy that he was ejected from.
A sadly literal instance. The stress of making the film caused producer Charles K. Feldman to develop heart problems, which claimed his life just two years after its release.
A less lethal instance happened to all of the film's directors except for John Huston. All of them had fairly distinguished careers prior to working on this film, but none of them had anywhere near the same success afterwards. Probably the worst affected was Val Guest; after word got out that he had taken over as the primary director late in production, he got unfairly blamed for the resulting mess and was reduced to directing Awful British Sex Comedies for the rest of his career.
Deleted Role: Ian Hendry was cut out of this project. All that remains of his role is a dead body being removed.
Descended Creator: John Huston originally wrote the role of M with Robert Morley in mind. When Morley was unavailable, Huston played the part himself.
Dueling Movies: It was released in the same year as an official Bond, You Only Live Twice. This duel affected the official release to the point where it became one of the factors in the long and bitter Broccoli/McClory legal feud that started a decade later and only fully ended in 2013, 7 years after McClory's death and nearly 5 decades from when You Only Live Twice and Casino Royale 1967 hit theaters.
The film's failure with film critics and Bond fans, it being responsible for producer Charles Feldman's death, and it becoming one of the roots of the ugly EON vs Kevin McClory rivalry tainted its reputation so badly, no other attempts were made to adapt Casino Royale until EON themselves used it as the starting point for their rebooted Bond series.
Hostility on the Set: The rift between Orson Welles and Peter Sellers was partly caused by the arrival on set of Princess Margaret, sister of Queen Elizabeth II. Sellers had known her previously and greeted her in an ostentatious manner to ensure all cast and crew noticed. However, the Princess walked straight past him and made a big fuss over Welles. Nonplussed, Sellers stormed off the set and refused to film with Welles again. It's also been suggested that the superstitious Sellers disapproved of Welles' use of magic tricks.
Troubled Production: Not only did an obscene number of directors and screenwriters get involved, but the actors fought with them, and with each other — the reason that Evelyn Tremble and Le Chiffre are not seen in the same shot during the Baccarat scene is that when they tried to get Peter Sellers and Orson Welles in the same studio, Sellers balked. He felt that Welles was not taking the scene seriously (remember that Sellers had wanted the movie to be the straight adaptation he was promised and was increasingly enraged over the continual slide into wacky parody the script was taking). Sellers was also an extremely superstitious man and took exception to Welles performing magic tricks during shooting, and finally refused to appear at the same time with Welles, forcing their lines to be shot at separate times.
Wag the Director: Peter Sellers caused many problems onset. He had actor John Bluthal (who was to play multiple roles) sacked, ordered a set torn down because he had a dream where his mother visited the set and told him she didn't like it, caused delays by leaving the set for days at a time, refused to be onset with Orson Welles and hired Terry Southern to write his dialogue (and not the rest of the script) to "outshine" his costars.
The producer had intended to cast Sean Connery as Bond, but balked at the star's paycheck demands ($1 million, which wasn't cheap back then). It is assumed that had Connery been cast, it would have been a straight 007 film rather than the parody it would eventually become. Years later, Connery ran into the producer and told him it would have been much better if he had agreed to the million-dollar paycheck.
An entire sequence involving Tremble going to the front for the underground James Bond Training School (which turns out to be under Harrods, of which the training area was the lowest level) was never shot, thus creating an abrupt cut from Vesper announcing that Tremble will be James Bond to Tremble exiting the elevator into the Training School.
At the start of The '60s, Feldman was able to get Howard Hawks interested in the novel, and there were some initial talks between Feldman, Hawks and Leigh Brackett about adapting it, with Cary Grant floated as a possibility to play Bond. Then they saw a preview screening of Dr. No and Hawks decided it would be pointless to even try doing Casino Royale, so he completely dropped the idea.