Really, that should have been the episode name.
Here’s something vaguely interesting. Originally, it looked like MLP:FiM was going to use the Dungeons and Dragons incarnations of monsters. The hydra, for example, is not the classic mythological version of a snake with many heads, but the middle ages Bestiary version that is more a giant lizard with many heads. And Dungeons & Dragons original author and editor, Gary Gygax, used the Bestiary version to build much of the monsters for that game. Now, FiM using D&D monsters makes a lot of sense, since Hasbro owns Dungeons & Dragons through Wizards of the Coast. It just makes things easier if you pull from a catalogue that you already own. However, the Chimera shown in Somepony to Watch Over Me deviates both from the D&D Chimera, and from the Mythological Chimera, becoming something of its own thing while having aspects of both.
The earliest record we have of the Chimera comes from Homer’s Illiad, where it is described as having the front of a lion, the middle of a goat, and the end of a snake, as well as it breathing fire. If you take *just* that description, you end up with a lion’s head, a goat’s body, and a snake’s tail, with the lion’s head belching out fire. Later on, in various statues, carvings, and writings, the description changes significantly, with a lion’s head, a goat head growing out of the middle of its back, and a snake head as a tail. Very likely this is what Homer meant, his description was just a bit vague. Often the snake is swapped out with a dragon and it’s the dragon’s head that does the fire breathing. Though in some writings, it’s the goat head that breathes fire for some bizarre reason. Another big point is that in Myth, the Chimera is a singular creature, much like most Greek monsters. There’s only one Chimera, and just for reference’s sake it’s female and possibly the mother of the Sphinx and the Nemean Lion of Heracles’ myth.
Interestingly, while everything we know about the Chimera comes from Greek art and writings, it was always said to have come from Lycia (an area that is now part of Turkey). But no Lycian art depicts the creature. This is an area rife with volcanic vents, so there are many places where the ground is always leaking fire, much like how the place Applebloom ran into the Chimera was belching fire all over the place.
Dungeons and Dragons:
The main differences between the Mythological Chimera and the D&D Chimera is again the D&D version is taken from the middle ages Bestiaries, and is shown to have the three heads (Lion, Goat, and Dragon) side-by-side, much like Cerberus the three-headed dog is depicted, plus the D&D Chimera is winged. Oh, and there’s lots of Chimeras. It’s a species. In this version the dragon head does the fire breathing. Over the various editions the art styles change significantly, and the Chimera became a ‘base’ creature where derivative creatures have a slightly different head line-up, but otherwise this Chimera is the standard. The goat head can be swapped out with a bull, the lion’s head with some other large feline, and so on.
Friendship is Magic:
So here the depiction differs from either of those. Instead of a lion, we have a sabre-tooth tiger head which is in a way a bit more visually interesting and is allowed for in the D&D chimera derivatives. The goat's head is tusked, and I'm not entirely certain what was going on with its horns, but I guess they felt the need to up the 'teeth' factor there. Instead of the myth’s goat head coming out of the middle of the back, it’s side-by-side with the tiger head like the D&D version. But the ‘dragon’ head is a very definitely a snake and is the creature’s tail, much like mythological one, not side-by-side with the other two as in the D&D version. And this version is not winged. It lives in a region with a lot of fire vents, and is probably resistant to fire, but it doesn’t seem to breathe fire itself.
And it might very well be a unique monster, but I get the feeling that it's meant to be a species, given how Applejack deals with it. (I was very amused by the ricotta cheese, though I would have recommended Tulum cheese as being more appropriate. But likely not available in Equestria.) it is, however, definitely female as the various heads referred to each other as sisters, so that maps to the mythological version.
Given this, and the inclusion of the Arimaspi in the The Lost Treasure of Griffonstone it’s pretty obvious that someone over there is a mythology nerd. They’re not using the D&D versions of creatures, nor are they using the versions that a basic level of Greek myth would indicate. They’re including details and odd information that is only available to someone who delves *hard* into ancient myths and legends, and yet are swapping out details (like the tiger head) to create something new of their own. Both episodes were written by different people, but I have no doubt there’s some form of collaboration going on and someone in there is throwing it details.