Created by Crockett Johnson, who is best known today for his children's book Harold and the Purple Crayon, the strip featured a cherubic-looking five-year-old and his far-from-cherubic fairy godfather, Jackeen J. O'Malley, a short, cigar-smoking man with four tiny wings.

The usually caustic Dorothy Parker had nothing but praise: "I think, and I'm trying to talk calmly, that Barnaby and his friends and oppressors are the most important additions to American Arts and Letters in Lord knows how many years.

A many of their adventures have surprising results, such as uncovering a gang of criminals hiding their loot in a supposedly haunted house, Barnaby's winning a scrap iron contest while out searching for a leprechaun's pot of gold, and unmasking a spy working in Mr. Baxter's office.

As time passes, more characters are added, including Jane Schultz, the little girl from down the street who didn't believe in Mr. O'Malley until she saw him; Gorgon, Barnaby's talking dog (who never talks in front of the adults); Gus, the timid, glasses-wearing ghost; Atlas the Mental Giant (who is physically Barnaby's size); and Lancelot McSnoyd, the annoying invisible leprechaun who speaks with a Brooklyn accent.

[1][3] The strip was briefly revived, with adaptations of the early stories minus their World War II references, for a run from September 12, 1960, to April 14, 1962.

Fantagraphics has begun publishing a five-volume series of collections designed by Daniel Clowes, reprinting the entire original run (1942–1952) of the strip.

[8] The play was later adapted for television as a 1959 episode of the General Electric Theater, hosted by Ronald Reagan and starring Bert Lahr and Ron Howard.