Cher auditioned for the role of 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".
Morgan Woodward was originally slated to play Frank Hamer, but he was held up when filming of Cool Hand Luke fell behind, so the part was given to Denver Pyle.
Arthur Penn originally turned the script down but after various other directors did likewise - including William Wyler - Warren Beatty was compelled to take it back to Penn. The director agreed only on condition that he could make some important changes, the main one being making Clyde impotent as opposed to bisexual.
Arthur Penn was particularly fascinated with the way Akira Kurosawa handled violent action and death in his films. In particular, he drew on Kurosawa's balancing of slow motion and real time that he employed in Shichinin no samurai.
Warren Beatty really wanted his then lover Natalie Wood to play the part of Bonnie Parker but Wood wanted to concentrate on her therapy at the time. She also didn't want to work professionally with Beatty again who she considered "difficult".
Warren Beatty wanted to produce this movie in black and white. This was rejected by Warner Brothers.
Jane Fonda turned down the role of Bonnie Parker. Living in France at the time, she did not want to relocate to the U.S. for the part.
Morgan Fairchild, who was active in Dallas theatre, began her film career in this film as Faye Dunaway's stand-in.
Michael J. Pollard admitted in later interviews that he borrowed his accent from Bob Dylan on the "Blonde on Blonde" album.
Michael J. Pollard didn't realize in eating scenes that you don't actually eat all the food because of the possibility of repeated takes. Sure enough, he soon regretted it in the scene in which the outlaws kidnap a couple and eat their lunch in the car. By the 12th take, Pollard was feeling decidedly ill, having had to eat 12 whole hamburgers.
Michael J. Pollard's character, C.W. Moss, is a fictional conglomeration of all of Bonnie and Clyde's minor sidekicks including: Ralph Fults (their first sidekick), William Daniel Jones (nicknamed "W.D." and "Deacon", and was an attendant at the gas station owned by Clyde's father), Ray Hamilton, and Henry Methvin (who's father made the deal with Frank Hamer to set Bonnie and Clyde up).
Gene Hackman regretted his decision to film Buck's death scene in his vest. The scene was shot several times out of sequence; when they came to complete it, winter had set in and Hackman had to play it in his vest in near-freezing conditions.
Gene Hackman was on the set one day when he noticed a guy standing behind him and staring. The man said, "Hell, Buck would've never wore a hat like that." Hackman turned around and looked at him and said, "Maybe not." He looked like an old Texas farmer. The man introduced himself and said, "Nice to meet you - I'm one of the Barrows."
A crucial fact left out of the movie was that Bonnie Parker was virtually incapacitated for the last year of her life from a car wreck. Clyde Barrow was driving fast down a lonely country road in Texas when he came upon a washed-out bridge. Unable to stop in time, the car went over the edge crashed and into the creek. The force of the impact jarred Bonnie's seat forward, pinning her in the car as it began to catch fire. She received severe burns on the backs of her legs that made it difficult to walk. She would either limp or was carried by Clyde. She was, in fact, injured at the time of the nighttime tourist court shootout and the field shootout (where Buck was killed) that occur near the end of the film.
A screening for Jack L. Warner went very badly for Warren Beatty and Arthur Penn - Warner got up three times to pee. Warner initially dumped the film into drive-in and second run theaters and apparently went to his grave still hating the film.
According to Warren Beatty in the Special Addition DVD documentary, in the death scene, the make up department fixed a fake scalp over his real hair with a line so that while he was being shot, it would look like his head was being blown off. Beatty says that partially the reason why he had the fruit in his hand was that the moment he squeezed the fruit was supposed to signal the make up artist to pull the line and rip the scalp off. However, when the scene was being filmed, the artist was so nervous that he forgot to pull the line. By the same token, Faye Dunaway mentions that the make up artists also put appliances over her face that were also wired so that when she was being shot they would yank off the flesh colored covers.
According to the film makers in the Special Edition DVD Documentary, the scene in which Clyde shoots the man on the running board marks the first time in film in which the shot being fired and the man being shot are both in the same frame.
According to the film's editor Dede Allen, the climactic massacre was meant to evoke Abraham Zapruder's footage of John F. Kennedy's assassination. As Clyde Barrow (Warren Beatty) goes to the ground in slow-motion, a fragment of his skull is dislodged by a bullet hit, a similar head shot captured by Zapruder's footage of the JFK assassination.