The Broken Ear: Part 1 - S2-E2
Other mistake: The villains lower a rope with a noose in it. They place it over a man's beard they believe to be Tintin. The noose is not tight yet, but it suddenly is when they pull on the man's beard, with no way for them to tighten it. (00:17:45)
Chosen answer: It is a pill that makes alcohol taste disgusting.