Continuity mistake: At the very beginning, when we see Brighty behind the waterfall (Ribbon Falls), in the farther full shot of the cascade, we can see Brighty moving his head to the left (our left) and downward. In the next shot a moment later (POV right next to Brighty under the cascade), his head is instantly higher than before, and is only angled slightly to the left.
Continuity mistake: At the beginning, right after the opening credits, Old Timer picks up a gold rock. When he first picks it up, we see a close up shot of his hand holding it only an inch or so above the ground. The very next shot a second later, from the side, shows his hand holding the gold instantly a foot or so above where it was before.
Continuity mistake: When Uncle Jim is talking to Homer about making moon lily tea, the position of the rifle in Homer's hands keeps changing between shots. In the side shots of Homer, Jim, and Irons, Homer is holding the rifle at an angle to the left; in the close front shots of Homer only, he is holding the rifle pointed straight ahead (toward Irons).
Continuity mistake: When Jake Irons and Brighty are crossing the Colorado River in the cage, Brighty freaks out and starts kicking at the wooden cage door. Before he starts kicking, the door is seen to be firm, intact, and unbroken, but in the shot of his first kick, you can see that before the hoof impact the door is already somewhat broken.
Continuity mistake: When Uncle Jim is reading the nameplate on his new rifle, his hand is right on the backside of the part with the nameplate. Then, in the closeup shot of the nameplate, his hand is suddenly gone.