Pony
Ponies were a sapient quadrupedal species which existed in various universes.
Biology
Ponies were quadrupedal and had "cutie marks". (PROSE: Jenny Everymare, etc.) Their fur varied in colour, (COMIC: Untitled, Peter's Death, etc.) and they could have wings. (PROSE: Jenny Everymare)
History
Pinkie Pie and Jenny Everywhere's universe
In one universe, Pinkie Pie and Jenny Everywhere were talking ponies. They once encountered each other and remarked on this. (COMIC: Untitled)
Kokotomo Island
On Kokotomo Island, Andrew Chapel was briefly transformed into a pony, to which he asked if there was a rule against him having hands in any of his potential forms. (COMIC: The Halloween Caper)
Jenny Everymare's universe
In one universe, Jenny Everymare was a version of Jenny Everywhere with white fur, wings, and an infinity symbol cutie mark. She was either native to Equestria, or arrived there after shifting from another universe. (PROSE: Jenny Everymare)
Losing Peter Griffin
In one universe, Twilight Sparkle was a pony with purple fur who lost Peter Griffin, visiting him on his deathbed in a hospital. (COMIC: Peter's Death) She later went past as a version of Jenny Everywhere promoted Gevity™ to the local version of Jenny, still in the hospital. (COMIC: Jenny Says: Drink Gevity™!)