Just so we are clear, I'm talking about projects about worlds with ponies in them, hence the tag "MLP-inspired". But still, it's cool people have tried worldbuilding.
While mine isn't necessarily pony-related, it's actually inhabited by anthropomorphic animals (or 'furries' for lack of a better term). The world they live in is like ours, but slightly more advanced.
The sapient population has a widely diverse range of species, such as different mammals (canines, felines, rabbits, rodents, bovids, equines, deer, mustelids, marsupials, bats, bears, seals, primates, cetaceans, etc), reptiles (lizards, crocs, snakes, turtles, etc), birds (sparrows, ravens, gulls, chickens, ducks, eagles, hawks, falcons, owls, etc), amphibians, sharks, and (still ambiguous on this) insects. That's not all though, there are also man extinct and prehistoric animals, such as Pleistocene megafauna, dinosaurs (theropods, sauropods, stegosaurs, ankylosaurs, ceratopsians, and ornithopods) pterosaurs, marine reptiles (plesiosaurs, ichthyosaurs, pliosaurs, etc), and synapsids. It doesn't end there either, there are also some legendary species that inhabit the world, such as dragons (westerns, easterns, wyverns, quetzacoatls, etc), griffons, phoenixes, kitsunes, unicorns, jackalopes, etc.