'Al Hill''s character is "Repulsive Rogan" in dialogue but "Filthy McNasty" in the credits.
After the first bank robbery, Og says that $50,000 was stolen from the bank and retrieved. Later in the day, he comes to the Souse' home and tells Myrtle that her father retrieved $25,000 in stolen funds.
During the car chase, after Egbert Souse' has removed the windshield, it is back on the car twice, first, after passing the woman on the road, and second, when the chase is finished and the car comes to rest.
Souse is reading an account of the robbery and one of the robbers is called "Loudmouth McNasty". At another point a policeman says his name is "Repulsive Rogan". However, in the beginning and end credits he is named "Filthy McNasty".
When Dr. Stall gives Snoopington the bottle of pills, he is holding his pipe in his hand. In the next shot, his pipe is in his mouth.
When Egbert punches the man trying to buy back the Beefsteak stocks from Og, the man is knocked back through a window. As he falls through, the whole wall, including what is supposed to be the brick building seen outside of the window, shakes.
Throughout the car chase at the end of the film, tires are constantly heard squealing and screeching, although the entire chase takes place on dirt roads and in fields, where tires wouldn't squeal.
When Snoopington is in the bank preparing to examine the books, the bank employee helping him is heard saying, "Let me give you a hand here", but the actor's lips are not moving.
When W.C. Fields enters the hotel room of J. Pinkerton Snoopington, a hand can be seen on the doorknob on the other side pulling the door shut.
Wires are visible when the workmen are thrown from the ditch they are digging by the police motorcycle.
In the opening bit of dialogue, one of the old ladies points out that there is an "accent grave" over the final e in a character's name, meaning it would be pronounced "Sous-AY", not "Souse". In fact, it's an accent aigu (or acute accent), in both pronunciation and painted on the mailbox she's looking at.
Egbert repeatedly describes the "assegai" as a knife or a sword. It is in fact a spear.