The Black Island: Part 2 - S1-E11
Revealing mistake: The mechanic the detectives presume to be a pilot says "This is my first flight". Thomson and Thompson turn their heads to each other whilst the mechanic speaks. Note how they have a black color in their eyes, but when they finish turning their heads, the color in the eyes of the detective on the left disappears for three frames, which reappears as soon as they turn their heads to the ground. (00:31:40)
The Black Island: Part 2 - S1-E11
Revealing mistake: Thomson and Thompson commandeer a plane. When the plane exits the screen in the shot where one of them says "Go up, go up", there are some sort of grey smudge marks on the screen that shouldn't be there. (00:31:25)
Chosen answer: If Hector was seriously intent on removing King Ottokar's scepter from the glass cage holding it and launching it through the window with the camera, then Hector would have been forced to knock out the two guards so they would not have interfered with Hector's plan as soon as he removed the scepter from the glass. As for Hector, himself, was explained when Tintin was explaining how Hector stole the scepter. Tintin placed a twig inside the camera and it launched out of the camera. Hector would have placed the scepter inside of the camera, and would have been knocked unconscious due to the spring effect created when the scepter had been launched.
Casual Person