As a puppy on the planet Krypton, where he had no super-powers, Krypto was the playful pet of baby Kal-El, the infant Superman.

As the hour of Krypton's doom drew ever closer, Superman's father, Jor-El, nursing the faint hope that his ongoing "experiments with small rockets" might yet save his son, launched Krypto into outer space in a tiny rocket as a final trial run, intending for the dog-carrying rocket to return safely to Krypton after making one or more orbits of the planet.

"By a cosmic mischance," however, "a meteor struck the trial rocket out of orbit" and sent it careening into space, and although Jor-El did succeed in launching his infant son toward Earth in the final moments of the cataclysm, Krypto appeared lost forever in the interplanetary void.

For years, the rocket bearing Krypto drifted through space, ultimately to arrive on Earth, where, like any native of Krypton, Krypto acquired super-powers like Superman's and was happily reunited with his beloved master, who was at that time a teen-ager growing up in Smallville in the home of his foster parents, Jonathan and Martha Kent.

Superboy the teenaged Superman - fashioned a cape for Krypto modeled after his own, and Krypto, now grown into a fully developed "superdog," became his frequent companion in super-heroic adventures.

Krypto's super-powers - including X-ray vision, super-strength, invulnerability, and the power of flight are similar, if not identical, to Superman's own, although his strength is undoubtedly not as great as Superman's, just as the strength of an ordinary dog is not as great as that of an ordinary man.

On the other hand, however, Krypto's super-hearing and "super-keen sense of smell" are probably more acute in a canine that in an ordinary human being.; Like any surviving native of Krypton, Krypto the Superdog is vulnerable to kryptonite.

Described as Superman's "faithful pet super-dog", Krypto is fully aware that his master, Superman, is also Clark Kent.

Krypto loves to romp and play in outer space, visiting distant worlds; cavorting in and about his Doghouse of Solitude, a large floating doghouse which he has constructed out of meteoric fragments and mischievously chasing comets, "just as Earth-dogs chase cars!"

In order to summon Krypto home from his distant wanderings, Superman either signals him by whistling at a highly pitched supersonic frequency which only Krypto's ears can hear, or else summons him by means of "super-ventriloquism," a ventriloquistic technique that enables Superman to throw his voice over exceedingly long distances.

On at least one occasion, when absolute secrecy is called for, the Man of Steel employes "supersonic ventriloquism," a form of super-ventriloquism in which Superman's voice is pitched so high that only Krypto can hear it.

Krypto, for his part, communicates with Superman by means of a special "barking code" similar to Morse code taught to him by Superman when the Man of Steel was a teenager.