In a French interview, Clint Eastwood said of this movie, "It was an old-fashioned theme, probably too old fashioned since the film didn't do as well as we hoped. But if, as a film director, I ever wanted to say something, you'll find it in Bronco Billy".
When the gang goes out to kick up their heels it shows them entering the The Ranch Club with the big horse in front. This is a real place, thats it's real name, and it's still open in Boise, Idaho. However, the interior that is shown is another bar, about 3 miles away called The Dutch Goose. It is also still open and there is still the hole in the door where lefty gets his hook stuck.
In real life, Gilbert M. Anderson, nicknamed "Broncho Billy", has been attributed as being the first ever movie star of the Western film genre. "Broncho Billy" lived between March 21st 1880 and January 20th 1971. In the film industry, "Broncho Billy" was an actor, writer, producer, and director.
Clint Eastwood's first film since Kelly's Heroes (1970) not produced by The Malpaso Company. Eastwood and Maggie Johnson were divorcing at the time, so the profits had to be shared with Johnson. Robert Daley set up Second Street Films to produce the movie.
Many of the actors Eastwood both directed and acted with earlier in his career are in this movie. Actress Sondra Locke and actors Bill McKinney and Sam Bottoms were all in The Outlaw Josey Wales (1976). Locke and McKinney were also directed by Clint Eastwood in The Gauntlet (1977) and were in the comedies Every Which Way But Loose (1978) and Any Which Way You Can (1980) without Eastwood's direction. Actors Geoffrey Lewis and Walter Barnes first worked with Clint Eastwood as actor/director in the western High Plains Drifter (1973). They would reteam as just actors in Every Which Way But Loose (1978). Geoffrey Lewis first worked with Clint Eastwood in Thunderbolt and Lightfoot (1974) and would work together again in Any Which Way You Can (1980) and Pink Cadillac (1989). Eastwood would later direct Lewis without appearing in Midnight on the Garden of Good and Evil (1997). Dan Vadis worked with Clint Eastwood in High Plains Drifter (1973), The Gauntlet (1977), Every Which Way But Loose (1978) and Any Which Way You Can (1980).
The insane asylum is located in old Boise on the VA campus. It has been many things but since the late 1980s it became an alternative high school. (I went to school there and love that it's also an insane asylum)
The make and model of the car that Bronco Billy drove was a 1957 Pontiac convertible according to publicity for the film though the IMCDb says that it is a 1960 Oldsmobile Super 88. Either way, the red painted vehicle is fitted with such chattels and fixtures as pistol door handles, bullhorns on the bonnet and fake upholstered cow-hide seat-covers.
Clint Eastwood's children acting in the movie are Alyson, who he was leading on horseback and then sitting next to him at lunch. Alyson asked him 'What did he do to make you so mad Bronco Billy'. While his son Kyle sat opposite and asked him 'So you killed one-eyed Charlie'
When Dr. Canterbury tries to lead the patients in a cheer for Billy, there is a close up of a man with long blonde hair and a beard. The man standing behind him was also the deputy in the scene in Sheriff Dix's office.