Bronco Bill
From superman.nu: Supermanica
Bronco Bill
Bronco Bill is the human identity adopted by Comet, the Super-Horse when under the influence of a comet. Bill is a rodeo performer due to his innate understanding of horses and perhaps due to the fact that, a) he was previously Biron the centaur and/or; b) he is Comet, the Super Horse.
Because his true identity is unknown to Supergirl, Bill enjoys a romantic interlude with his Mistress of Might.