The Secret of the Unicorn: Part 2 - S1-E4
Continuity mistake: Tintin, Haddock and Snowy are walking down the street and Haddock says he's going to be rich and tosses his hat in the air. There is a lamppost right next to Tintin. A man then opens his window, telling Haddock to keep the noise down and Tintin is suddenly standing about a foot away from the post. (00:26:20)