He was never bred.
He slept on set until someone said, “Quiet on the set.” At which time he woke up ready to act. Then, at the word, “Cut,” he relaxed.
Roy Rogers attributed Smiley Burnett with the name, Trigger.
Trigger was housebroken.
Gene Autry’s Champion the Wonder Horse(s), there were three. Things a writer would need to know:
He had stunt doubles.
His hoof prints are next to Autry's handprints at Hollywood’s Grauman’s Chinese Theater.
In addition to such normal tricks as playing dead and jumping through rings of fire, all three of the horses could dance the hula and the Charleston.
He (they) had their own television show.
Silver(s) Two horses shared the role of Silver, Clayton Moore’s horse in The Lone Ranger. Moore personally chose Silver #1. Things a writer would need to know:
Silver #1 was used when scripts called for a gentle horse.
Silver #2 was the only horse with which Moore toured.
Silver had a chase-scene-and-stunt double named Traveler. Those chase scenes were made with Traveler’s owner, Bill Ward, riding him.
In his old age, Silver#1 made head shots.
Scout, the horse Jay Silverheels rode as Tonto, could outrun Silver and had to be reined in.
Buck was the name of Matt Dillon’s horse. He never saved Dillon’s life or led the way to a hideout. However, Dillion rode several horses in Gunsmoke. His deputy, Festus Haggen, rode a mule named Ruth. Doc once called his horse, Popcorn.
Careful writers, such as Katherine Pym, do their research. Longfellow would approve, once saying, “It takes less time to do a thing right than to explain why you did it wrong.”
Sadly, with the demise of westerns came the demise of famous horses.