Bevendre

Cowpony AJ concept. NSFW versions with and without udder are here.

How about Rainbow Dash? We haven't seen a pegasus cowpony yet.

Anonymous

Pegasi who become cowponies tend to have a harder time adjusting to the change, in part because of the more severe change in size with the average cowpony being just shy of 7′ tall whereas the average pegasi is just over 5′ tall, and in part because of the loss of their wings. Pegasi turned cowponies tend to have a relatively uniform coat with spattered patching on their lower half, and horns that are located above and behind the ears that exhibit a more prominent downward curve than other subspecies.

(draw marble pie as cowpony, she'd be the cutest one)

Anonymous

Not all cowponies have extreme proportions, nor are all too confident. Earth ponies turned cowpony have their horns placed above their ears, and many tend to grow longer horns than those developed by their unicorn-cowpony kin. Coats are generally more uniform in color than other subspecies of cowpony, but a flare over the nose, or a large patch over the back or belly are very common.

A couple changes to cowponies in the new run of Raricow:

A cowpony does not develop an udder until they become pregnant. As soon as an egg is fertilized the udder begins to form.
In Raricow cowponies are infectious through bodily fluids, though the contagion is in such negligible amounts that it is only really possible to “catch” the affliction through direct consumption of tainted fluids.
It is possible to drink from a cowpony for a time without changing, but once the changes have begin they will progress to completion
If a bullpony (male who becomes a cowpony) drinks heavily from a cowpony they run the risk of becoming a female cowpony. Again, they can drink without changing, but if the changes start they will finish
Lactose intolerance acts as an effective immunity to the infection through milk. The body is unable to break down the milk and so the magic dies.
The source of the magic infection cannot tolerate cold, so chilling stored milk will remove the infection from the fluid, but heating it may reactivate the infection after which it can remain viable for some time..

How to tell cowponies apart from minotaurs:

A cowpony has two fingers and a thumb on each hand, each digit tipped in a hard keratin hooflet. A minotaur has four fingers and a thumb on each hand, and all digits are dexterous and without a thick nail.

The horns of a cowpony are centered around the middle of the forehead, over the eyes and are generally small in females, but much larger in males. The horns of a minotaur are on the sides of the head above the ears and are generally large in males and females, though males tend to have slightly larger horns.

Cowponies typically have mottled coats that are relatively uniform throughout their body. Minotaurs have a clear divide around their midsection with thicker, darker fur beneath the navel.

While large male cowponies can reach up to 8 feet in height (including horns) most cowponies are around the same average height as Earth ponies, averaging about 6 feet. Minotaurs on average stand upwards of 9 feet (including horns) with females rarely more than a few inches shorter than males.

Cowpony milk does not make one become a cowpony, unless it is consumed directly from the source. Cowponies are not a normal race and, though they can breed and have natural born calf-foals, the most common way for cowponies to reproduce is for another to become a cowpony, becoming milkborn.