Factual error: Tintin says they only have one bullet left. That bullet is in the magazine,and since it is a semi automatic, there should also be one in the chamber, meaning they would have two bullets. Even if they only had that paticular bullet, he doesn't cock the gun, meaning the chamber would be empty and therefore wouldn't fire.
Factual error: Towards the end when the smugglers are trying to takeoff from the airport with the float coming at them, Marcel (the lead smuggler) tells Tipa (the fat smuggler) to pull up because they're about to hit the float. Tipa quickly pulls back on the flight controls to takeoff. The scene switches to an outside shot of the plane's wing where the "flap" moves to the down position, but pulling back on the controls manipulates the "elevator" (on the tail) which would cause it to pivot upward. The flaps are controlled separately. (01:20:40)
Factual error: In the credits, there is a paper revealing that Mater was knighted on Tuesday, July 15th, 2011. However, July 15th, 2011 was on a Friday, not a Tuesday.
Factual error: The "Great Terror" turns out to be a giant goose, but you see in the shot inside the castle that its footprint is not webbed, even though geese have webbed feet.
Factual error: The term mayor of Paris was abolished from 1871 till 1977. But we see Victor Maynott wants to join the mayor campaign in 1910.
Factual error: The 'Mayor' says he's a Turtle, but he's actually a Tortoise. Turtles have paddle type limbs for swimming, not reptile like paws as depicted in the movie.