Factual error: In the scenes set during 1918, Clive is shown wearing a typical late 1930s/WW2 military production British steel helmet with its distinctive canvas covered sprung chinstrap.
Continuity mistake: When Jerry launches his egg carton, there are initially three light bulbs in the back, but when he releases the bulbs, there are now four.
Other mistake: Holmes appears disguised as a Sikh, complete with turban and beard. Although his face is black, his hands are without any make up and are white as snow.
Continuity mistake: When Droopy is standing the door, he tells the convict he's going to call the cops. At this point you can see there is nothing next to Droopy on the frame, but in the very next shot a hinge has appeared.