Without question, Hergé's Tintin and René Goscinny and Albert Uderzo's Asterix were the most successful French-language comics of the twentieth century. Despite their very different eras and styles, it seems inevitable that characters from each should have met. In Tintin et les Picaros (Tintin and the Picaros, above), someone in an Asterix costume passes (look near the palm tree). Mickey Mouse and others may also be found in the carnival crowd. Goscinny and Uderzo replied by having dead ringers of Tintin's dead ringer detectives, Dupond et Dupont (known to English readers as Thompson and Thomson) appear, appropriately, in Asterix chez les Belges (Asterix in Belgium). Thanks to Guy Harvey for tipping me off.