Artist’s description from DA:

Ponies use an interesting system of both magic and more traditional means for reproduction. This added to the range of sexual preferences has lead to a range of hybrids that are not all that uncommon in the general public. unlike most hybrids in nature the offspring produced in these pairings have a good chance of being fertile themselves leading to populations of 2nd or more generations. Though first generation hybrids do have a higher chance of infertility the most.

medical it’s hard to treat Hybrids do to their complex anatomy, few doctors have the training or will to treat them. Hybrids also have trouble getting transplants or blood since it’s harder to find matches. This Leads to doctors who can treat Hybrids usually having they lists filled with hybrids. (Gear being one of them)

Social Hybrids are not always seem as equal, a common slur being mule and old medical term.

do to the wide range of sizes even within the same hybrid type, size charts aren’t helpful.

Dragon-pony: most of this hybrids are 5 or more generations apart from the dragons themselves, the tend to be larger then most ponies. not all have wings but most have horns. Dragon-ponies need meats in their diet.

Plant-ponies: some plants have strange magics and will lure ponies in from time to time. the offspring tend to not need to eat as much as other ponies, due to them producing food like plants. many are earth pony like traits, even those with “wings” can rarely use them. only first generations of this types exist, though they live a bit longer.

Spiderpony-ponies(lol): The most common hybrids due to male spiderponies mixing well with ponies. their also common in spider tribes them selves, since most mistake them for pure spiderponies they don’t get as much trouble. they need to eat meat.

Sea serpent-ponies: Like Dragon hybrids few are first generation, and they live mostly in seapony cities. they need to eat meat.

Seapony-ponies: very rare do to seaponies rarely even meeting land ponies, sea serpent ponies are more common, they need to eat meat.

Breezie-pony: These ponies rarely live past childhood, becoming more or less brain died once they reach adulthood. luckily this hybrids are so rare that they are more a myth then a fact.

Hippogriffs (griffon-pony): not uncommon, do to some immigration of griffons in the past few years. They are very stable mixes showing some traits each time, their a bit taller them most pegasuses and never show unicorn or earth pony traits. they need to eat some meat.

Donkey-ponies: rarely fertile, these ponies tend to be very hardy, more so then ether parent.

Zebra-pony: very like donkey ponies, they usually have stripes.

other notes:

changling-pony: do to changlings not having reproductive organs and them rarely wanting deep relationships on changling mix has been seen.