EDIT: Added possibility of triplets produced from alicorn pairs. I am fully aware that fertilized eggs don't split in thirds for triplets, I just don't have a better way to describe it at the moment and after doing two full charts of these and explaining everything in detail, I'm tired. If you know the correct phraseology for triplet eggs, cool beans, I'll change the chart if you can tell me. Just don't be a jerk in the comment section, okay? It's a freakin' children's television show. Real World limitations don't apply and hey, pobody's nerfect. The fandom is about love and tolerance, so verbal attacks on my intelligence are immature and against everything the show teaches in the first place. I did the best I could to explain it; if that's not enough for you, then do something better and show me up. Idc. I'm cool with that as long as you're having fun.
UPDATE: Included Faust confirming the ponies themselves can in fact crossbreed, for those of you insisting that they cannot. Also included some extra info for each subheading. Lastly created another chart for mixed blood ponies, which you can see here: [link] for all you Derpy x Dr. Whooves people who believe Sparkler and Ditzy Doo are their children. This second chart proves it's possible if Derpy has a unicorn in her ancestry!
This chart can help you create family trees for your pony pairings--trace how traits transfer from your pairings to their children and show you what children can be produced from what kinds of pairings.
Male ponies are in BLUE
Female ponies are in PINK
Foals are in PURPLE, and are genderless (as they can be either gender)
Unicorns have RARITY HAIR and a HORN
Pegasi have RAINBOW DASH HAIR and WINGS
Earth ponies have APPLEJACK HAIR and a HAT
so that you can tell them apart
A chart of what kind of foal will be produced depending on the genetic traits of both parents.
This chart assumes that the pony parents are pure blooded unicorns, pegasi, earth ponies, and alicorns If a foal is a unicorn when one parent is a pegasus and the other parent is an earth pony, then that means that one of its ancestors MUST have been a unicorn, and that the genetic trait skipped the parents' generation and became apparent in the foal's generation. Therefore, for an example, you can still produce a pegasus from two earth ponies--but only if there was a pegasus further back in its ancestry, otherwise this would be impossibru.
Genetic Chart Explained:
Unicorn + Unicorn = Unicorn
Pegasus + Pegasus = Pegasus
EarthPony + Earthpony = Earthpony
Unicorn + Pegasus = 50% Chance of Unicorn foal, 50% Chance of Pegasus foal
Pegasus + Earthpony = 50% Chance of Pegasus foal, 50% chance of Earthpony foal
Earthpony + Unicorn = 50% Chance of Earthpony foal, 50% Chance of Unicorn foal
Unicorn + Earthpony = 50% Chance of Unicorn foal, 50% Chance of Earthpony foal
Pegasus + Unicorn = 50% Chance of Pegasus foal, 50% Chance of Unicorn foal
Earthpony + Pegasus = 50% Chance of Earthpony foal, 50% Chance of Pegasus foal
ALICORNS (Winged Unicorns)
This is where it gets a little tricky.
Alicorns are a combination of all three pony types-- UNICORN, PEGASUS, and EARTHPONY all at once. Now according to pureblood genetics, the original three above (earthXearth, pegasusXpegasus, unicornXunicorn) this means that an alicorn could theoretically mate with any pony type and produce a foal. However, the alicorn would act as the second unicorn when mating with a unicorn, the second pegasus when mating with a pegasus, or the second earth pony when mating with an earth pony, because it possesses all three types of pony magic. The other two types of pony magic would lie dormant, but not be all visible at once in the foal.
Alicorn x Unicorn = Unicorn
Alicorn x Pegasus = Pegasus
Alicorn x Earthpony = Earthpony
Because basically in each pairing, the single-type pony's genes would match with the same genes of that type which the alicorn possesses, and the other two magic traits the alicorn possessed would lie dormant instead.
With Alicorn x any other pony type, the type of pony the second pony is would determine the nature of the foal because it would present a 100% match gene-for-gene, while the other two pony traits would lie dormant as they would only be an unmatched 50%.
Alicorn x Alicorn = Alicorn
^ This is the only situation in which another alicorn could be produced from a pairing, because both alicorns would be matching each other trait for trait.
In other words, SINGLETRAIT + SINGLETRAIT = SINGLETRAIT, whereas SINGLETRAIT + DIFFERINGTRAIT = 50/50 CHANCE OF TRAITS.
In an alicorn x alicorn pairing, it would basically be unicornXunicorn, pegasusXpegasus, and earthponyXearthpony all at once, and each trait would then be present in the foal.
We can safely assume that Alicorns can indeed mate with all ponies because of Prince Blueblood's relation to the alicorns by word of Goddess (A.K.A. Lauren Faust) who said he is the "great great great great great great great great great great great (and probably even more greats) nephew on Celestia's and Luna's mother's side, about 52 times removed, roughly speaking." Since he is a unicorn and not an alicorn, meaning he must have unicorn blood in him along with alicorn blood. Since the name "BlueBlood" literally means to have Royal Blood, it is also safe to assume he is directly related to the alicorns and not adopted into the family as some may claim. Particularly including the fact that this is a children's show, it is difficult to believe that he was adopted into the royal line or that an ancestor of his was adopted into the royal line, as this would certainly have been explicitly mentioned somewhere in the show as it would be a plot device for sure. However the possibility of adoption was not ever stated or even implied, and along with his name literally meaning Royal Blood, we can assume he is in fact a descendent of alicorns who does not carry wings or lay claim to earth pony magic.
I considered adding zebras to the chart because of Zecora. However, because we do not see any striped pegasi or striped unicorns, or even any Zebra x Earth pony pairings, it is difficult to say at this time whether Zebras can even mate with ponies or alicorns at all. I am not going to hazard any guesses at this point. I think what I have in the chart is logical and feasible however.
Because dragonoskis are just so different from earth ponies, unicorns, pegasi, and alicorns in every way, I'm going to say that it's highly unlikely that a dragonoskis could ever mate with any pony type and reproduce successfully.
This does not mean that Discord could not mate with any pony type, it only means that he and his partner-of-your-choice could in all likelihood never reproduce, simply because they are too far removed in terms of animals. You don't see mice mating with eagles, because they cannot bear children together, and so I think it would be with a dragonoskis and a pony.
The flashbacks in Season 4 might suggest that Celestia and Luna were born alicorns (or that the animators didn't bother making new puppets for a few scenes), and from the expanded media (ie: a book), I guess I could infer that Cadance (a Pegasus) and Twilight (obviously, a Unicorn) both had the inhibitor for being an alicorn, but the inhibitor wasn't activated during conception (maybe activating the inhibitor is a very rare occurance), and Celestia merely activated the dormant mutation in the genes of both to give them a horn and wings, respectively. Though, if this is the case, the gene would have had to have been in Twilight's own bloodline for it to pass on to her, meaning that there's an alicorn somewhere on her family tree; if there wasn't, she couldn't have had the inhibitor in her genes at all; Blueblood is related, but obviously didn't have the gene activated.
There's only two "pureblood" alicorns, and one other "mutt" alicorn; so that means either A) There are more alicorns than just Celestia, Luna and Cadance for Twilight to be related to, which I find doubtful, or B) Twilight is, in some way, related to either Celestia, Luna or Cadance enough to have carried the inhibitor over. The latter seems more likely, especially since alicorns are rare, so that could suggest Twilight was a blueblood even before she became good friends with Celestia; her parents could have been aristocrats even before Shining Armor married Cadance or Twilight was coronated.
So, if we take Lauren's logic with Blueblood and use it with the inhibitor hypothesis, Twilight Sparkle could well be at least somewhat related to Celestia or Luna; since they seem to be the first alicorns known to ponykind. But this is just me hypothesizing, nothing totally concrete.
I think all of it is entirely logical, well-thought-out and well-reasoned. And I love the idea of Alicorn x Alicorn maybe = triplets.
<?xml:namespace prefix = da /> mah brain
tough < < i have to say in the episode "baby cakes" the nervousness of both the cakes made it seem more like a mature joke hidden in the show ,that the younger viewers wouldn't understand anyway, that the little ones may or may not be from mr. cake at all < <......not judging or anything but just saying
So I'm going to say that it's likely that you could get an earth pony, pegasus, unicorn, or alicorn in probably equal probability--but I would guess that the chance of you breeding out an earth pony would be higher since Alicorns do have some earth pony in them since they're a mix of the three types.
Of course there are numerous combinations that could genetically occur, perhaps meaning the legs would be solid and not holey at all, while the horn and wings are retained but perhaps not at all or fully usable and look to be so. My biggest problem in thinking about this is the body chemistry itself though--the holey legs, because I feel like they wouldn't support a heavy mammalian body, which I'd assume is a dominant trait for ponies that aren't pegasi.
So let's say an Alicorn was once a unicorn and mated with a unicorn. That would make a unicorn.
Unicorn Alicorn x Pegasus = Unicorn or Pegasus
Nopony is born an alicorn...
Also, the breed is not "alicorn"
They are literally a breed known as "princess"
Twilight turns into one and what do her friends say? "You look just like a Princess"
And apparently you automatically become a Princess upon gaining the horn and/or wings? That technically makes the breed name canonically "Princess" rather than "alicorn" which is admittedly a false term in the first place, as it refers to the horn of a unicorn, and not, in fact, a unicorn with wings attached to its back.