His first appearance was in "Topolino" #1353 (1981) in the story "Paperino e il turista spaziale." He is an alien who came from space, and more precisely from the planet Duck, with hisspaceship shaped as a coin and that can be shrunk to the size of a dime and reads O.K. Quack's fingerprints as a means of activating its size mechanism. He also appeared in some other stories such as "Zio Paperone e il satellite bomba" ("Uncle Scrooge and the exploding satellite") from "Topolino" #1354, "E quando Paperino prende una decisione..." ("And when Donald gest up with a decision...") from "Topolino" #1373; "Zio Paperone e la moneta disco volante" ("Uncle Scrooge and the flying coin"); "Zio Paperone e la piramide capovolta" ("Uncle Scrooge and the pyramid upside-down").
In all of these stories O.K. Quack is looking for his spaceship that has been lost and is circulating as a dime somewhere in Duckburg. O.K. Quack soon reveals his strange abilities such as telepathy (talking to locks, flowers or anything else) and telekenesis (moving things with the power of his mind, included the money bin). He doesn't understand or appreciate need or use of money (in this way he seems to have been inspired by Bill Walsh and Floyd Gottfredson's Eega Beeva). Franco Fossati once defined him as "...a perfect character who with his innocence criticizes the absurdity of our society. Going on with time he will adequate to our times and to our every-day way of living and we'll forget that he came from space." Uncle Scrooge, Donald Duck and the Nephews know that O.K. Quack is a space alien and are actively trying to help him find his ship. They first met him in the money bin where he entered talking to Scrooge's locks and was looking at Scrooge's coins thinking that they were all spaceships. Thus he does not require any cover story and can freely act in his strange ways (at least in front of them). He sometimes lives in the Money Bin, and sometimes in a rented room in a small hotel in Duckburg where he met Umperio Bogarto (no official American name as of June 2010), a sorry private detective whose services O.K. has contracted to also help locate his spaceship.
As for his initials "O.K." there has been no real explanation and it is assumed that they basically mean the same as the American expression, "It's all right!"