Revealing mistake: During the dancing scene, Jamal shows the percussionist how to use the tambourine first, then tells him to start drumming, so he puts the tambourine down. However when he cues in the guitar, the tambourine starts to play again with the drums and guitar. A few shots later, with the tambourine still playing in the background, you can see the percussionist's tambourine sitting on the table next to him where he had left it.
Continuity mistake: There is a scene about 2/3 of the way in the movie where you see Jamal (Martin) standing by the lake and his chain is under his shirt, he looks back into the forest and his chain is hanging out of his shirt, then he goes back to the lake and his chain is under his shirt again.
Factual error: There is a scene where we can see several flags hanging on the wall of the castle. These are supposed to be flags in the Middle Ages. However, one of them is the present day banner of the Hungarian Republic (where part of the movie was shot).
Continuity mistake: When Jamal is held prisoner, he is in a small cage, barely able to move. In the next scene, however, the cage is twice as large, with plenty of room.
Continuity mistake: When the woman is putting a rag on the head of unconscious Jamal, she notices the medallion around his neck and holds it to look at it. When he suddenly sits up, the medallion is tucked into his shirt.
Other mistake: When Martin Lawrence falls over the railing in attempt to get the mysterious necklace, the camera goes to another shot that pulls away from the moat. You can see the logo on the back of Lawerence's cover-alls swimming away at the corner of the screen, when he's supposed to be under water.
Continuity mistake: When Victoria is in Jamal's room wearing only a sheet, her hair is in front of and behind her shoulders between shots.
Continuity mistake: When Jamal is trying to ride a horse for the first time, he rides to a stable. When Jamal leaves the stable, he has wheat on his shoulders. He takes it off, but in the next shot he has wheat on his shoulders again. Then in the next shot he does not have wheat on his shoulders anymore.
Revealing mistake: When Knolty and Jamal first are walking into Knolty's home, their shadows are toward the right and forward. A few shots later, Jamal's shadows can be seen on the bushes behind him, facing the opposite direction from before.
Visible crew/equipment: When Jamal first visits Knolty's home, after he saves his life, shots switch between Jamal, Knolty, and the two together. The first time the shot switches to Jamal alone a crew member's arm is visible in the bushes behind and to the left of Jamal.
Plot hole: When Jamal saves Knolty's life and is invited into his home, he leaves his work jacket at the lake shore. This jacket is where he kept his spray-paint. However, later in the movie Jamal has somehow recovered his spray-pain.
Other mistake: When Jamal and Victoria are on top of the castle, Victoria shouts, "Don't do it Jamal" then has her throat cut. If you look carefully, you see there is no cut made and the blood only appears when she rolls over on the floor.
Factual error: Towards the end, when the medics are reviving Martin Lawrence, they are using a defibrillator. You can hear the sounds of the defibrillator charging and then discharging. They then show Martin Lawrence wake up, but he is fully dressed. In order for a defibrillator to work, it must come in contact with the skin. I doubt they had enough time to redress him after using it on him.
Continuity mistake: When Martin first sees the castle, you can see the knights turning to the castle but then from the guard's point of view the knights are further back on the path.
Continuity mistake: After Jamal saves Knolty's life, Knolty is sitting up on the ground. In a shot from behind him, his arms are holding him up, however when it switches to a shot from his front, his arm appears on his chest though only a split second later.
Continuity mistake: At the end of the movie when Jamal has been pulled out of the water and taken care of, his clothes go from entirely soaked to completely dry. They CANNOT dry that fast, in that amount of time.
Continuity mistake: When Jamal is standing next to the guards when he arrives to the middle ages, small cabins are visible, but when the rebels are attacking, there's a wide shot of the field in front of the castle entrance. No cabins are visible.
Plot hole: The legend of the black knight (in this film) is that he can breathe dragon's fire. Jamal somehow rigs up his aerosol spray-can inside his helmet to shoot out the flames. However, there are three problems with this: one, how did it fit in the helmet? Two, how did he activate the spraying mechanism without his hands? And three, how did he even ignite the spray?
Revealing mistake: In the final battle scene, Jamal is hitting one of the soldiers with his leg. As the soldier falls, it's clear that he throws himself back intentionally.
Factual error: In the 14th century, Normandy was an enemy of Britain's. There is no way a Duke from Normandy would marry an English princess.