Certainly, we don't see animals beyond the context of the mane six, but likewise, we don't see ANYthing that doesn't pertain to them. After all, we don't see perytons either, nor have we cause to suspect that Griffin society is as we've imagined. These concepts, and indeed all concepts, were permitted for no other reason than that the community envisioned them mutually enjoyable. Succeeding all of these, we ought to expect specific reasoning for why certain concepts might not be allowed. What might be thought fun for all isn't something we could ever guarantee consensus on, but there are a few principles that root them. Primary among them: Does a concept agree with the themes, values, and settings of the show? And failing that, does it at least not violate them? In addition, we consider "gameplay," or balance. Might a concept unfairly favor some players over others? To the first, do we see animals having adventures of their own on the show? No. Do we know them to exist unattached to ponies? We do. We see them in the everfree forest, for instance (and it is mentioned as well, in fact, that the creatures in everfree live untamed). We see them rescue Fluttershy prior to her residence in ponyville. And where it is not explicit, it appears implicit that animals have lives of their own, including potential adventures. The world is likewise as perilous to animalkind as it is to ponykind, after all. As for the final clause -- gameplay -- most animals would not appear to unbalance gameplay or roleplay. Bears and lions might warrant caution, perhaps, but a bird probably can't harm anything. So my question is this: what about the concept of animal apps warrants special consideration beyond those of others? As I see it, they might be considered as perytons. Given that perytons at least appear uncommon, we are cautious of allowing everyone to play one (although most people will want to play ponies, given that is what they see the most of on the show anyhow), but with just a few people at it, it's just a fun option. Given that animals can't speak, I suspect that their attraction will be limited (except for the comanions specifically featured on the show) and that there will be no need for special moderation.