The Crab with the Golden Claws: Part 1 - S1-E1
Revealing mistake: When the Thompson's discover that Tintin is rummaging through the bins in order to find the Crabe Extra tin, one of them says "Tintin. Whatever are you doing?" and the other detective is shown stopping next to Tintin, altering the position of his cane. As soon as he stops altering the cane, the bottom of the cane is shown, through Tintin, overlapping with the bin. (00:04:15)