Revealing mistake: In the scene out West with the buffalo, notice the car driving in the distant background.
Factual error: The movie takes place in the early 20th century (1910s or 1920s or so). When Dean and Jerry are riding in a RR cattle car with its doors open you can clearly see parked automobiles from the 1950s through the open door of the train car.
Visible crew/equipment: In the scene where George takes Samantha into the lounge room to lie down, as she reclines on the lounge you see the shadow of the boom microphone on the ceiling moving.
Continuity mistake: When Frankie punches Barakov, pushing him through the window, not only do you see the wires lifting him, but it is obvious that the inside of the building is a studio set as not only does the window get broken, but also the wall above it is torn. The wall is obviously made of paper and the scenery outside the building is a painted backdrop. And when the angle changes to outside the building, only the window is broken but the wall is intact.
Continuity mistake: When Cluck Trent is telling us about Aardvark Ratnik, he is holding a paper cup in his left hand. When he says "This looks like a job for Stupor Duck!" we cut back to Trent, and the paper cup has disappeared.
Continuity mistake: When we see Dorlock Holmes at his desk at the start of the cartoon, you can see that he is writing with the feather in his right hand, but in the next shot he is holding the feather with his left hand.
Continuity mistake: When Foghorn Leghorn is relaxing in the barnyard, you can see there are two hens fanning him, but when a man on a bicycle arrives with a telegram, the hens with fans have disappeared.
Continuity mistake: When Napoleon takes some snuff, he puts the box back on the map, but in the next shot the box is now on the table near Bugs.
Continuity mistake: When the Coyote has put on his Batman outfit, you can see behind him there is a boulder and an empty box before he is about to jump. But we see the Coyote on top of the cliff in the next, the boulder and box are nowhere in sight.