The Calculus Affair: Part 2 - S1-E13
Continuity mistake: When Tintin and Haddock walk through a corridor with two drunk men, Tintin opens a door. The key hole on the door is blue. For a few frames, the key hole becomes brown, then back to blue again. As he closes the door, the key hole is once again brown for a couple of frames. (00:34:50)