In general, cronopios are depicted as naive and idealistic, disorganized, unconventional and sensitive creatures, who stand in contrast or opposition to famas (who are rigid, organized and judgmental if well-intentioned) and esperanzas (who are plain, indolent, unimaginative and dull).
He does refer to them (in one of the early stories Costumbres de los famas) as "those greenish, frizzly, wet objects," but this description is just the initial author's vision of the invented character.
Cortázar first used the word cronopio in a 1952 article published in Buenos Aires Literaria reviewing a Louis Armstrong concert given in November of that year in the Théâtre des Champs-Élysées in Paris.
References to cronopios in Cortázar's work occur in 20 short sketches that make up the last section of Historias de Cronopios y de Famas as well as in his "collage books," La vuelta al día en ochenta mundos and Ultimo Round, which were collected in a French edition he considered definitive.
The term cronopio eventually became a kind of honorific, applied by Cortázar (and others) to friends, as in the dedication to the English-language edition of 62: A Model Kit: "This novel and this translation are dedicated to Cronopio Paul Blackburn ..." (Blackburn translated several of Cortazar's early stories under the title The End of the Game.)