Conversation so far:
what was the pre-crisis comet?
Comet the Super-Horse is a fictional character that appears in comic books published by DC Comics.
what comic books does he appear in?
Comet was introduced in the Superboy story in Adventure Comics #293 in February 1962.
Are there any other interesting aspects about this article?
Comet was one of a series of super-powered animals, including Streaky the Supercat and Beppo the Supermonkey, that were popular in DC's comics of the 1960s.
did he win any awards?
A traditional equine Comet is partially seen in Legion of Three Worlds #1.
He is part of a display in the museum Superboy-Prime visits.
what comics was he in?
appeared regularly with Supergirl beginning in Action Comics #292 in September 1962.
who did he work with?
Comet was Supergirl's pet horse.
when was he created?
Comet was introduced in the Superboy story in Adventure Comics #293 in February 1962.
what was his best attribute?
As he described to her telepathically, he was originally a centaur in ancient Greece named Biron.

Question: why did he change?
Self-contained rewrite: why did  Pre-Crisis Comet change?