Throughout the movie, the name of Ava Gardner's character is spelled Lillie Langtry. In the end credits, it is spelled Lily Langtry.
When Judge Roy Bean goes out to the front of the courthouse to apologize to the women for calling them "whores", he takes his hat off and holds it against his chest. In the next shot, his hat is still in his hand. It subsequently returns to his head.
When Judge Roy Bean speaks to Grizzly Adams, he holds his gun over his leg and in front of his chest, in turns with the changes of the camera angle.
When they bury the bear, the gravestone indicates the bear was about 3 years old and died in 1899. That would mean that the visit to the town by Grizzly Adams would have occurred around 1896. That would be impossible since Grizzly Adams died in 1860.
Louis XIV had only six children with Marie, and only one of those lived to adulthood. He also had 13 known illegitimate children.
When Roy runs the owner of the whores out of town, his shadow on the ground appears to be midday or early afternoon. Five minutes later, after Maria shoots at him and he follows her, the shadows are extremely long as near sunset.
When Bean visits San Antonio to see Lilly Langtry several steel drums are visible in the alley behind the theatre that are of a design not available until the early 1930s.
When Bean regains consciousness in the alley behind the theater, he pushes over a modern, round, galvanized garbage can.
Narration said 1855. The Colt revolvers were Model 1873 Colt Peacemakers. Wrong. Nothing in this takes place in 1855. Per the opening storyboard, it starts in the 1890s; the ending takes place in the 1920s.