Character mistake: After Maverick gives the "actors" their hundred dollars, he says "News travels fast in the Old West." Why would he refer to the west as "old" when, for him, it's the present? This is an expression that didn't come about till later on, when the west BECAME old.
Suggested correction: This was a joke, since it's a comedy movie.
Character mistake: When Gordon describes Leonardo Da Vinci's idea for a flying machine, he mentions Da Vinci designed it in 1540. However, designs for Da Vinci's flying machines were dated as early as 1488 and Leonardo Da Vinci died in 1519.
Character mistake: After running into Indians on his last patrol, Capt. Brittles orders Sgt. Tyree to head south and meet up with the (indicating singular) Paradise River Patrol. He is then to proceed at his best pace to meet up with Capt. Brittles at the stage station. Capt. Brittles states that he will approach the objective from the east. Sgt. Tyree is then shown riding off perpendicular to the unit's line of march. After a brief time lapse, the unit meets up with another patrol of soldiers that once again identifies itself as the Paradise River Patrol. This Paradise River Patrol joins up with the larger body of troops and continues toward the stage station. No sign of Sgt Tyree. Upon arriving at the stage station, Capt. Brittles meets up with Sgt. Tyree and another body of soldiers which is also identified as the Paradise River Patrol.
Character mistake: At the ravine, upon learning that the bridge doesn't exist yet, Marty states to Doc "We can't wait a year and a half for this to be built". If you carefully look at the sign, it says the bridge is opening Summer 1886. That's under a year away, not a year and a half from Sept. 1885.
Character mistake: When the posse is heading out in the morning, one guy says that it's heading north and they start riding in the direction he's pointing. However it's supposed to be first thing in the morning, and you can see the shadows of the horses cast to the left of screen while they are riding towards the camera. The sun rises in the east, which would be right of screen with the shadows cast towards the west. Since they are riding towards camera, this puts them heading south.
Character mistake: During the military parade, check the lady behind the soldier on the left. She can't help stare at the camera the whole time before the soldiers arrive. (00:07:03)
Character mistake: John Ruth never mentioned to anyone in Minnie's Haberdashery about a letter from Abraham Lincoln! So how could Oswaldo ask Chris Mannix about it? Oswaldo just couldn't have known.
Character mistake: In the opening scene when the bandit is going for his trigger finger, Billy is seen with his eyes slightly open in the background. His eyes are then shown to open suddenly with dramatic effect. (00:05:50)
Character mistake: Gene Wilder as the rabbi leaves the Torah on the floor of the porch of the home of the synagogue president. A rabbi would never put a Torah on the ground.
Character mistake: The oldest boy says "Here comes the calvary" instead of cavalry.