Les Aventures De Jo, Zette Et Jocko is a Belgian, French-language adventure comic book series created, written & drawn by Hergé in response to a 1935 request by Father Courtois, the director of the weekly French newspaper Coeurs Vaillants, who asked for a more wholesome alternative to his extremely popular Tintin that would embody classical family values.
As such, Jo and Zette, a brother and sister, are much younger than Tintin and their family unit is firmly established. And while they embark on adventures just as wild as their Hergé's more famous creation along with their pet chimpanzee Jocko (inspired by a popular toy of the time), they often depend upon adult intervention to get themselves out of a jam.
The first two adventures were published periodically in Coeurs Vaillants and Le Petit Vingtième between 1936 and 1939 and were only republished in album form (two per adventure) in the early fifties, after which Hergé released a third adventure. In the sixties, Hergé charged close friend and collaborator Bob De Moor to reenginner a discarded Tintin story written by Greg, Le Thermozéro, as a Jo, Zette & Jocko adventure. The project was never completed and is said to currently exist in a state similar to Tintin Et L'Alph-Art, the unfinished final Tintin story.
The initial two stories were republished in 2003 as two special black & white albums recreating their original newspaper presentation, while a complete color edition regrouping all the the published works was released in 2008. It should be noted that despite album publication order, Le Rayon du Mystère (issues 3 & 4) is actually the first adventure, initially published between October 22, 1936 and March 10, 1938 while Le Stratonef H. 22 (issues 1 & 2) is the second, initially published between March 31, 1938 and November 9, 1939.
Translations exist in Dutch (by Casterman), Danish ( by Carlsen Comics) and English (by Egmont, Mammoth and Methuen).