Continuity: In the scene just before the final attack on the castle, D'Artangan is surrounded by his fellow Musketeers. He gets off his horse and while doing so there is a tight close up where you see clearly that he is wearing his Musketeer outfit that he threw down on the floor in the previous scene. When he finishes talking to the horse (and he is back in his normal clothes) Porthos hands him the Musketeer uniform, which D'Artangan then puts on.

Continuity: At the beginning of the movie, D'Artagnan is shown as a child with the old man who raises him. Soon after it is 14 years later - the old man is wearing the exact same clothes and there are no changes to his appearance.

Factual error: In 17th century France a peasant would not be using metric mesurments. Just before the final battle, D'Artangnan states the castle is 2 kilometers away. Metric was developed by French scientists AFTER the revolution.

Visible crew/equipment: In the scene after Tim Roth and his men have taken Queen Anne, the camera looks out of the estate and down a dirt road. A ways down the road it turns to asphalt.

Other: When the burial of D'Artagnan parents begins, there is a shot from below, showing a beautiful view of the top of some trees, and the sky. There are 2 jet contrails visible.

Continuity: While the character Mena Savari plays is in the credits as Constance, she is referred to as Francesca many times throughtout the movie. In fact, I can't recall a single time she is referred to as Constance.

Other: Right before Febre kills the man who let D'artagnan escape, you can see a road sign made of metal in the background. They didn't make road signs like that back in that time.

Plot hole: Musketeers were the elite shock troops of the King's army, armed with costly muskets. Strange that not one of them actually had a musket, let alone fired one. They only had a few pistols.

Continuity: Young D'artangan speaks with an accent. His older self does not.