Darcy refers to Camembert and Desiree as the Duke and Duchess de la Plume de ma Tante to Sir Rodney before they arrive at the ball at Ffing House. After this they are always referred to as the Count/Countess.
When Camembert, Bidet and Desirée come across the girl and soldiers in the Chateau, the girl is plucking a harp and singing. Right before Camembert tells them to stop, the soldiers sing "Yeah, yeah, yeah!" The girl's mouth is moving, but the soldiers' mouths don't move.
After the duel in the Garden of Fragrance, Sir Rodney asks Pommfrit where the Bastille is. But he had in fact been there earlier in the film, masquerading as a soldier, so he should already know where it is.
Sir Rodney wedges his snuff box into the guillotine as the Duc De Pommfrit is about to be executed. After he has been hustled away, the snuff box is much higher up and stops the blade dropping anywhere near the Duc's neck.
When the message girl runs on the platform to give the Duc De Pomfrit his message, he tells her to throw it into the basket. In the next shot it disappears. Later, when Ffing tricks Camembert into executing Malabonce, the letter reappears.
In the Chateau Neugf, just before the fights scene, Sir Rodney climbs up onto the banister and his right arm holding his sword is by his side. In the next shot, his right arm is held up. When the soldiers give chase, his arm is by his side again.
Pommfrit swings out of a window during the fight scene in the Chateau Neuf. When he re-enters, he starts fighting a soldier with a black hat. When the soldier smashes the bottle of wine with his sword in the next shot (and for the remainder of the fight), the hat is gone.
Pommfrit throws a stone bust at Bidet in the Chateau Neuf. He falls unconscious on a rug. When Pommfrit goes to pick up a chair (which he smashes on a soldier's head) the rug is seen but Bidet is not visible.
When Camembert unfolds the Black Fingernail's calling card in his office, the shot of him doing it shows all four of the fingers of his left hand behind the paper. When we see that it is the calling card, his index and middle fingers have moved in front of the paper.
Sir Rodney and Darcy blow open the door to the Chateau Neuf with a barrel of gunpowder, using a trail of powder as a fuse. The fuse works and the barrel explodes, despite the fact that there are clearly breaks of several inches in the trail where it climbs up the steps to the door.
Sir Rodney has his right hand right next to his snuff box after he slots it into the guillotine runner. In the next shot, his right hand is higher up and further away from the snuff box than it was without him moving his hand.
When Pommfrit is talking to the three women at Ffing House, he says he was face-down on the guillotine and later "the knife came hurtling down and bounced off the back of my neck" which implies he was facing downwards when he was actually facing upwards. However, Pommfrit is making up details as he is going along to make the story sound more gripping and heroic, such as the basket full of heads and the made-up fight where he allegedly kills six or seven soldiers.
Throughout the film, the name of the girl Sir Rodney loves is not revealed. However when Sir Rodney is trying to find a way to get into the Chateau Neuf, he calls her Jacqueline. When does he find out her name?
When the Duc De Pommfrit is standing next to the fountain, water is flowing out of it. In the following shots of the Duc talking to Desiree Dubarry, the flowing water has turned into a solid plastic rod.
When the several soldiers get out of the coach outside the Bastille, the coach can be seen quite clearly rocking from left to right which would suggest that soldiers are boarding through one door (out of shot) and coming out the other (in shot).