Factual error: The picture of Eddie and Teddy on the road with dad, supposedly taken in 1906, shows a Ringling Bros and Barnum & Bailey circus poster. In 1906, the Ringling Brothers circus and the Barnum & Bailey circus were two separate circuses playing in different parts of the country. They did not combine the two shows until 1919. (00:27:00)
Factual error: Look carefully at the electric trolleys trundling around the streets (and that Valiant hitches a ride on). You'll see that although they have boom arms on top, which are usually hoisted up and connected to overhead powerlines, there are no overhead wires anywhere for them to be getting electricity from. [Notice in the scene when Valiant gives Dolores the check, a Red Car Trolly passes outside the window and sparks fly from the overhead wire contacts. In all of the scenes outside the bar the wires are gone]. (00:10:10)
Factual error: The Goofy cartoon Roger watches in the theater was made in 1949, but the film takes place in 1947. (00:59:50)
Factual error: When Eddie throws Roger into the bar's storeroom (after Roger was breaking plates on his head), there's a Lucky Strike ad poster with the slogan "Be Happy, Go Lucky." However, the Be Happy, Go Lucky ad campaign didn't start until after 1948 when BDO took over advertising, and the film is set in 1947.
Factual error: In the bar scene where Judge Doom is looking for Roger, there is a pinball machine that can be seen on the right side of the stairs as Roger and Eddie are running out of the bar. Electromagnetic pinball machines of this design were not around at the time of this film's setting. The pinball machine is a Gottlieb Hurdy Gurdy (1966) model.
Factual error: When Doom reaches into the cab of the Dip vehicle and starts it, it doesn't jump. It is a modified military vehicle, and it's a standard. If you try to start a standard vehicle without pressing the clutch in to disengage the gears (the weasel driver left it in gear when he died), then the vehicle would lurch forward as the engine turned over.
Factual error: The red cars are seen traveling with poles raised on both ends. The wheel at the raised end of the pole, which collects power from the wire, must always be trailing the car. Basically, streetcars going forward have the rear pole raised and front pole lowered, and vice versa. They would not be traveling at normal operating speeds with the front pole raised, as that would damage the wiring system.