Continuity mistake: When Jacquouille and Lady Ginette are driving the car after the supermarket, Lady Ginette has sunglasses on during one shot from behind, when they are going to pass by a crossroad. She doesn't have them during the rest of the scene.
Audio problem: In the Middle-Age, when Godefroy and the wizard Eusaebius are talking about time travel and the 7 plagues of Egypt, there's two shots from behind Godefroy. He talks, but we hear nothing.
Continuity mistake: When Godefroy and Jacquouille are drinking wine in Cora's castle, the color of Godefroy's wine changes from dark red to pink during the scene.
Continuity mistake: When the old couple is trying to escape from Godefroy, the road is in the fields but in the following shots, they are in the forest.
Continuity mistake: When Lady Ginette takes the wine bottles to the kitchen, she doesn't takes her bags but when Jacquouille goes to see the television, her bags are gone.
Continuity mistake: In the opening scene, when Godefroy reappears in Middle-Age, he is going to shoot an arrow at the Duke, thinking it's a bear. He remembers what the wizard says to him and turns his body from right to left to avoid hitting the duke and to hit the Witch but in the close up of the arrow, he turns from left to right. It's not due to a different camera angle.
Continuity mistake: When Jacquouille travels to the Middle-Age, he is transformed in "a brown stuff" that fell on the car. Later, when he returns in modern time, the stuff is almost completely gone, but nobody could have washed it because they didn't notice the water in the car.
Continuity mistake: When Jacquouille is annoying the fireman that are trying to extinguish the fire, the hose of the chief on the edge of the window keeps changing place.
Audio problem: In the Middle-Age, when Jacqouille is stealing clothes in the tailor shop, the saleswoman says to Jean-Pierre, with the voice of Jacquouille "Qui es-tu, demoiselle?" (Who are you, miss?).
Continuity mistake: Before hiding the jewels in the freezer, Jacquouille removes almost everything in it but when Lady Ginette finds them, there's a bag of frozen vegetables on the cigar box.
Continuity mistake: When Lady Ginette takes some bottles of alcohol in the bar and Béatrice interrupts her, the ashtray that was on it disappears.
Continuity mistake: When Ginette is reading a magazine in the kitchen when everybody is trying to extinguish the fire, there's a bottle without tag and a sausage on the board. The sausage disappears in the next shot and a tag appears on the bottle. And after that, there's many bottles.
Continuity mistake: During the fire, Jacquouille throws equipment everywhere, thinking it will helps the firemen. Sometimes the pipes are brown and sometimes they are red.
Continuity mistake: After Jacquouille and Lady Ginette enters the house, Béatrice prepares the table. She takes some dishes and a green tablecloth. When she put it on the table, it is beige.
Continuity mistake: When the police chief is talking to the doctor, he holds a pair of briefs in his hands. He doesn't have them in some shots.
Revealing mistake: When Jacquard is being tortured by the Inquisition, the water is not poured in his mouth, the pipe in which the water really flows is sometimes visible.
Continuity mistake: After Jacquard has been tortured by the Inquisition, the pipe is in his mouth in some shots and besides him in others.
Continuity mistake: In the opening credits, there's many images of the first film. One of them is the children of Béatrice and Jean-Pierre. In the actual scene, it was only the boy, and it was in the night.
Revealing mistake: I think this film has been translated, so this mistake is surely only in the original French version. When Jacquouille and Godefroy are in the car with the old couple, Godefroy is sick and says "Je vais vomir glairer". Glairer is the old word for vomir (vomit). It's like he forgot to speak in old French for a second.
Continuity mistake: Jacquard's torture clothes are torn. They are not when he reappears in modern time. They are torn again when he shows him to the chief of police.