The clueless and clumsy detective duo of Thompson and Thomson are among Hergé's finest creations. They were based on his own father and uncle who were identical twins who sported bowler hats and carried canes.
Despite their incompetence they are entrusted with important missions across the world which they prepare themselves for by adopting the stereotypical costume of the relevant country. In this way they hope to blend in but invariably stick out like sore thumbs.
They first appear in the Tintin adventure The Cigars of the Pharaoh, in 1932, where they are referred to as X33 and X33b.
In a Tintin play of 1941 Hergé names them Durant and Durand but they later become Dupont and Dupond in the French.
Do you know which is which? Well Thompson has the full droopy moustache and Thomson the one that curls up at the ends. Here they are in the first U.K. edition of The Blue Lotus, published in 1983.