Continuity mistake: Riding with the mule in the passenger seat, Harold finds himself unable to control his car. Driving the wrong way, he instinctively crosses his arms as a car nearly crashes against him. In the next shot he has just one arm raised and the other already controls the steering wheel. (01:08:05)
Continuity mistake: Everyone sits down on the pillows for dinner. Harold's future father in-law grumbles about his sacroiliac pain, and his wife brushes him off saying "Oh Anthony, your back hasn't bothered you in years." Her purse is in a different position in her lap between shots. (00:44:20)
Factual error: Fakrash is a genie who served under King Solomon and he himself says that he's been imprisoned for 3'000 years. Yet the whole aesthetics of his clothes, decoration, architecture is the stereotypical Arabian Nights one, which would be several centuries posterior to his times and almost as foreign to him as the present day one.
Visible crew/equipment: An angry aspiring home buyer tosses a tomato inside the office of Fakrash and Ventimore, but the rancid veggie boomerangs on him when the genie summoning his powers reverses the flow of time causing the tomato to fly where it came from. Well, that's the idea, while in fact you can see a literal stagehand actually throwing the tomato in the actor's face. (01:17:55)
Other mistake: Mrs Kenton and Sylvia can't get into the study where Mr. Kenton is; there is no reason why the door would be locked. A mule can't lock it with a key and there is no debris or furniture to block the door. Harold opens it just fine from the inside without operating any particular kind of lock.