The swinging doors to the saloon completely disappear after Yosemite Sam orders "all of you skunks" to "clear outta here".
When Bugs dares Yosemite Sam to continuously step over lines that he draws in the sand with his foot, the last one that he draws causes Sam to step over the edge of a cliff and fall, then it cuts to a scene of him falling. When it cuts back to Bugs at the top of the cliff, those last lines that he had drawn are all gone.
After Yosemite Sam loses the card game to Bugs Bunny, the latter runs off-screen right. Up until that point in the cartoon, Bugs is wearing a big, yellow hat. In the next shot, his hat has disappeared and is not seen again until after Sam hits the ground (and is flattened). When Bugs goes behind the rock formation and reappears on the horse, he has the hat on. It disappears for good after Bugs wins the hand of Gin Rummy.
As Bugs Bunny and Yosemite Sam start towards each other in their initial duel, Bugs' gun belt is below his tail. When they come face-to-face, his gun belt is above his tail.
Yosemite Sam supposedly hits the "shooting gallery cowboy" seven times (There are seven "dings".), but only six shots are seen/heard, and only six "credit points" show up on the overhead scoreboard; "credit-for-hit" #4 dings twice.