The Calculus Affair: Part 1 - S1-E12
Revealing mistake: Tintin says to Professor Topolino it wasn't Calculus who tied him up. The next shot shows a timer on a bomb ticking. As each second ticks, the minute hand on the clock keeps ticking backwards or forwards. (00:17:50)
The Calculus Affair: Part 1 - S1-E12
Revealing mistake: The villain holds a syringe and some liquid comes out of it. It's plainly visible that there is no liquid in it. Syringes are see through - we should have seen the liquid. (00:06:05)
The Calculus Affair: Part 1 - S1-E12
Revealing mistake: The villains stand in front of Marlinspike Hall. The shot after a close-up of their feet shows the clouds along with a storm. Look to the lower left corner and you will see part of the grey cloud doesn't have any color on it, like the animation cell has been scratched. (00:02:50)
Chosen answer: It is a pill that makes alcohol taste disgusting.