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What was pre-crisis DC Comics' Comet?
DC Comics' Comet was Supergirl's pet horse and, while in his human form as Bill Starr, her brief boyfriend.
What was DC Comics' Comet like pre-crisis?
Comet was originally a Grecian centaur named Biron, turned horse by the witch Circe who originally wanted to turn him into a human. She gave him superpowers, including immortality.
How did DC Comics' Comet change into human form?
When Comet went to planet Zerox with Supergirl, a magic spell was cast that turned him human, but only while a comet passes through the solar system he is in.
Are there any other intresting aspects about the DC Comics' Comet article?
As a human, Comet adopted the identity of Bronco Bill Starr, a rodeo trick-rider, whom Supergirl fell in love with.

Question: who did he work with?
Self-contained rewrite: Who did DC Comics' Comet work with?