The Castafiore Emerald: Part 2 - S3-E8
Revealing mistake: When they are watching the news broadcast on Calculus' high definition television set, after the news broadcaster mentions Castafiore's stolen jewel, Castafiore says "He's talking about me." The mole on her cheek appears and vanishes from her face whilst she is saying the line, revealing a slip-up in the animation. (00:35:00)
The Castafiore Emerald: Part 2 - S3-E8
Revealing mistake: After Calculus has finished the high definition television broadcast, Tintin and Snowy are lying on the grass. When the scene starts, a bird is shown flying into frame and continues flying, but whilst it is on-screen, the bird suddenly vanishes from the frame. (00:36:30)
Chosen answer: It is a pill that makes alcohol taste disgusting.