Character mistake: On the day Rebecca arrives home, Junior Douglas says that he was "Valedictorian, Class of '95." Earlier, Drago talked of almost killing Running Buffalo "during that trouble back in the '40's," which would have been about 50 years earlier. That would mean Drago and McLintock were fighting Indians when they were babies, or possibly before they were born!
Continuity mistake: In one of the funnier scenes of the movie, a tipsy John Wayne attempts to escort Maureen O'Hara up a flight of stairs while drinking from a bottle of whiskey. They fall to the foot of the stairs, and the bottle is empty. After bopping Wayne on the head with the bottle, O'Hara throws it against the wall, and it's miraculously full again.
Continuity mistake: In Kate's hotel room, when she's trying to get away from GW she steps backwards through the hotel room's doorway onto the porch, and falls straight through the broken wood railing, but when GW looks down at Kate on the pile of hay, there's now a window behind GW, not a doorway, and clapboard siding has suddenly appeared on the hotel wall as well.Super Grover
Continuity mistake: When Kate's trying to hide from GW she heads to the restaurant which has double-hung style windows with muntin bars, and red curtains across the windows' lower portions, but in the interior shots the red curtains have vanished, and when Kate jumps out the window it's now just a single pane with muntin bars used for the stunt.Super Grover
Continuity mistake: When McLintock et. al. head to the clay slide, which is just outside of town, to check out the report of a kidnapped girl, it is very early in the morning. When they arrive, there is an argument, the girl shows up, and there is a brief fight, then they head home. But when they arrive home it is late at night.
Revealing mistake: After GW recruits Bunny to help the chiefs to escape and to acquire rifles and ammo, he comes home asking where the Katie with light red hair is. Katie, excited, goes out on the bedroom landing and sees him at the bottom of the stairs again asking where the woman of the house. Is. Just in back of GW, you can see the shadow of Mrs. Warren waiting to talk to him. Mrs. Warren then appears to try to tell him she was quitting her job.
Revealing mistake: When Agard is lifted and dumped into the oil mining cart during the brawl at the clay mud pit the cart is pushed towards the pit, and in the wide shot as the cart rolls toward the camera we can see the rope attached to the bottom of the cart pulling it, just before Agard falls out.Super Grover