Goofs

When Snoopy and the rest of the group are going through security check, Lucy is in front of Peppermint Patty instead of Marcie. After they pass through security, Marcie reappears in line before Peppermint Patty.

After dropping Peppermint Patty and Marcie off at the farmhouse, Snoopy and the boys apparently have to drive for a long time and distance to get to the chateau. But later when Charlie Brown runs for help when the chateau is on fire, the farmhouse the girls are staying at is now just right down the road close enough to reach within a few minutes by running and with the chateau being visible from the front door.

When Woodstock turns off the car wipers, they are completely down. But when Snoopy exits the car to investigate, the wipers are standing straight up.

When Linus and Charlie Brown wake up in the stable, Linus remarks that they are going to be late for school, and a watch appears on his hand. The watch then disappears a moment later.

When Snoopy enters Wimbledon, no one is there, and no one is sitting in the arbiter's chair that is later heard making the calls leading Snoopy to deflate it.

The color order of the French flag is inverted. The flag as depicted at the end is displayed with red on the left-hand side (the one closest to the flagpole), white in the middle, and blue on the right-hand side. The French tricolor flag is blue on the left-hand side, white in the middle, and red on the right-hand side.

When the French girl shows Linus the photo of Charlie Brown's grandfather during the Great War it is in color. It should have been in black and white.

When in the French classroom, "papillon" is misspelled as "papillion".

When the rental car breaks down in the town near the bakery, Peppermint Patty has Charlie Brown go get bread and certain fixings to make sandwiches. One, Charlie only buys the bread and nothing else, and two, even with him losing his share of the bread in the hood of the car, Charlie should not have been left unable to eat at all due to the mysteriously appearing sandwich fixings. He could've eaten the meat and cheese rolled up or something.

In the opening classroom scene where Linus and Charlie Brown stand and declare their trip to France, both Sally and Lucy can be seen. Sally is Charlie Brown's younger sister, and Lucy is Linus's older sister, so they wouldn't be in the same class or grade as their brothers.

Charlie Brown, Linus, Snoopy, and Woodstock are standing outside the château knocking on the door. We hear Linus say, "Let's get out of this rain.", but Charlie Brown mouths the words instead.

In London there is a "Travel Center", spelled the American way, rather than "Centre".

When Charlie Brown and Linus are selected to go to France, Peppermint Patty can be seen among the students congratulating them. Later, we find out Peppermint Patty goes to a different school and has no idea "Chuck" has been chosen.

Snoopy's first-class dinner menu on the flight to London includes "lamp cutlets".