Comet, the Super-Horse
The super-powered white stallion, endowed also with the power of communicating by telepathy, that is the loyal equine companion of Supergirl, periodically accompanying her on her adventures. Comet the Super-Horse was once Biron, a centaur of ancient Greece in the time of the great mythological heroes. One day, in gratitude for Biron's having thwarted an attempt by the evil wizard Malador to poison a spring where she drank, the enchantress Circe agreed to fulfill Biron's heartfelt wish to be transformed from a centaur into a real man, but Malador had tampered with Circe's potions, and the one that Biron drank transformed him, instead, into a horse. Circe had no means of undoing the tragic mishap, but she did partially compensate the hapless Biron by endowing him with "magical super-powers" as well as with the ability to communicate telepathically. Malador's vengeance on Biron, however was not yet complete—he banished the super-steed to a planet in the constellation Sagittarius, keeping him imprisoned there by means of a "magic aura."
Biron remained on his prison planet for more than 3000 years, waiting helplessly for freedom, until the happy day when the rocket carrying Supergirl toward Earth from doomed Argo City passed by the planet, its "repeller rays" shattering the magical aura and enabling Biron to escape. The freed super-horse flies to Earth, locates Supergirl, and establishes telepathic contact with her. She names him Comet, and he becomes her pet and her frequent companion in super-heroic adventure (Act No. 292/4, Sept 1962: "The Steed of Steel"; Act No. 293/2, Oct 1962: "The Secret Origin of Supergirl's Super-Horse"). Because Comet is not weakened by Kryptonite or affected by red sun radiation, he is an extraordinarily powerful being and he often acts in situations where Supergirl's powers would be compromised.
At the conclusion of one adventure, Prince Endor of the planet Zerox, a world inhabited by sorcerers, rewards Comet for his help by endowing him with the power to assume human form temporarily whenever he is within sight of a comet. At such times, Comet adopts the secret identity of Bronco Bill, a cowboy (Act No. 301/2, Jun 1963: "The Secret Identity of Super-Horse!").
Comet the Super-Horse wears a flowing red-and-yellow cape modeled after Superman's which is attached to his body by means of two wide blue straps. He is a member of the Legion of Super-Pets. When Metropolis television station WMET-TV inaugurates its new "Our American Heroes" series with a program honoring Superman, "our greatest American hero," Comet appears on the show along with three of the other super-pets—Beppo the Super-Monkey, Krypto the Super-Dog, and Streaky the Super-Cat—to help pay tribute to the Man of Steel (Act No. 309, Feb 1964: "The Superman Super-Spectacular"). In April 1965, Comet journeys through the time barrier to the mid-nineteenth century to help Superman and the other super-pets teach a well-deserved lesson to "cruel junkman" Cyrus Atwill (S No. 176/1: "The Revenge of the Super-Pets"). (TGSB)