The Secret of the Unicorn: Part 1 - S1-E3
Continuity mistake: When Tintin is about to buy the model Unicorn, there is an antique sale visible in the background. When Tintin says "Will you take 20 dollars?", a grandfather clock is shown, displaying 5:05. A couple of shots later, Sakharine pushes Tintin out of the way and the time suddenly changes to 2:00. (00:03:25)