Ali Baba and the Forty Thieves (1944)

Plot hole: Jamiel delivers Ali Baba's ransom note to Hulagu Khan by throwing a knife, and the shocked Khan and his guards look to the window. Since Jamiel does not duck away immediately, he should have been seen and identified immediately, but nothing of that sort happens.

Factual error: At the end, Jamiel climbs one of the palace towers and, as a sign of victory, hoists the Arabian flag. Only thing: Baghdad was located in Persia (today's Iran and Iraq), not Arabia; and the shown flag, the green 'shahada', did not appear until the late 18th century. The ancient Persian flag, as far as I could find out, showed a star.

Revealing mistake: When Abdullah escapes his Mongolian pursuers by jumping his horse across the ravine, the horse kicks loose some debris at the edge. But the rocks simply disappear, indicating that the ravine is a painted set-up.

Trivia: Hulagu Khan (1217-1265) was the grandson of Genghis Khan, and the brother of Kublai Khan, perhaps the two most famous Mongol lords. He conquered Baghdad in 1255.