Romance on the Set: Averted. In contrast to his infamous womanizing, Warren Beatty did not have an affair with Faye Dunaway. They agreed to remain platonic for the sake of the film.
Screwed by the Network: Attempted. Warner Bros. - and Jack L. Warner himself - considered the film an unwanted and unpleasant gangster flick doomed to bomb and treated it accordingly, giving it a limited release. Even after the film turned into a runaway success, Jack L. Warner was said to have carried a hatred of it until his death.
Sleeper Hit: Warner Bros. thought that the film would bomb, feeling that nobody would want to cheer for the outlaws in a gangster flick, and dumped it in August and offered Warren Beatty 40% of the gross as a result. Upon release, the mixed critical reception seemed to bear out their fears. But when young people started raving about it to everybody in earshot, it turned into one of the biggest films of 1967, and remains a classic.
Wag the Director: Warren Beatty and Arthur Penn quarrelled constantly during filming, as the star questioned almost every one of the director's choices. As a result, the rest of the cast often spent hours waiting for them to settle their differences. One major bone of contention was Penn's insistence that they add a scene in which Bonnie and Clyde pretend to be dead. Beatty insisted the idea was ridiculously pretentious, but Robert Towne tried to write it anyway. The writer soon realized that Beatty was right, but cautioned him to avoid a confrontation on the matter. In his opinion, Penn was only holding onto the idea out of insecurity - he couldn't admit he was wrong. After a few weeks of filming bolstered Penn's confidence, Towne was sure he'd drop the idea, which is exactly what happened.
The writers of this film originally hoped to they could get either of the great French New Wave directors to helm this film, François Truffaut or Jean-Luc Godard. Unfortunately, after helping develop the script, Truffaut ultimately decided to direct Fahrenheit 451 instead and Godard made unreasonable demands when the producers were courting him.note Supposedly, he wanted to shoot the film in New Jersey during winter, and was deeply offended when they refused. Given his disposition towards Hollywood, he was likely seeing just how much they would let him get away with. So Arthur Penn, whom Truffaut had recommended, did it instead.
Natalie Wood, Warren Beatty's ex-girlfriend (one of many actually), was considered for the role of Bonnie - and incidentally was actually a lot closer to the real Bonnie's physicality (they were both short ladies).
Bonnie and Clyde were originally supposed to have a bisexual relationship with their driver, but that was changed when Arthur Penn felt that would have defused the audience sympathy, leading them to be dismissed as "perverts" because they are criminals and ultimately harmed the story. There were also rumors that Warren Beatty was unwilling to portray a bisexual and ruin his image and there was the fact that The Hays Code would never have permitted it in the film in the first place.
Before deciding to play the role himself, producer Warren Beatty's first choice for the role of Clyde Barrow was Bob Dylan, who, at the time, bore a physical resemblance to the actual Clyde.
Warren Beatty wanted to shoot this movie in black and white. This was rejected by Warner Brothers.
Cher auditioned for Bonnie Parker, but when her husband/manager at the time, Sonny Bono, heard about the audition, he was furious at Warren Beatty for letting his wife audition for such a "controversial film".
Tuesday Weld was offered Bonnie and came very close to accepting before deciding it would interfere with her newfound role as mother. With Beatty as Clyde this would've been a reunion of Thalia Menninger and Milton Armitage.