In theory, we humans like spending time with other humans. In practice, we often spend the majority of our time with other humans thinking about all the nasty things we’re going to say about them once they’re gone. This doesn’t necessarily mean we don’t enjoy spending time with them, but you could argue we’re enjoying it for the wrong reasons. Now, pets, on the other hand, to them you can say exactly what you’re thinking, because they don’t speak more than a few words of [YOUR LANGUAGE HERE]. They can’t judge you, because they aren’t sentient, or if they are judging you, you’ll never know.
My assumption is that anthropomorphism springs from a subconscious wish to combine the two. This is not proper psychology, but it sounds like it, and that worked for Sigmund Freud, didn’t it? I don’t care that the ancient Egyptians thought they were putting animal heads on their gods because those gods used those animals as symbols. The truth is, without a shadow of a doubt, that a high priest just looked at his wife’s cat once and thought, “Damn, it just sits there looking all composed, yet somehow vaguely displeased with me. Just like the missus, come to think of it. What if they were the same entity?” And there you have it. That’s where Bastet came from. Don’t even try to argue that point, because we’re discussing Egyptian religion, where worshippers called the gods into being each day. What I am doing is simply continuing their tradition by calling this particular moment into being. I am literally correct because I say so.
What this means to us today is that, in order to have something that’s not a human but not just a talking animal, writers will often create some awful bastard from various parts of the two. The most popular form of this is ‘animal head on warped bipedal frame.’ These bipedal frames usually don’t have locking knee joins, so how it is they can stand in place so comfortably is a mystery. For some examples, see the stereotype lizardman/cat person looks. Another favorite is to take a human or humanlike torso and stick it in between a differing amount of animal features. Mermaids are the lower end of this; some other examples include snakes with arms and centaurs, both of which make even less sense. Just think about it: a centaur is 90% of a horse’s body, fused with 50% of a human one. How does this math function?!
Can you use these options? Absolutely so. I use them myself. I won’t tell you which ones, mind you- that would be quite improper. That, and coming up with a novel form of anthropomorphic character is a soul-crushing experience; it’s the brainstorming equivalent of listening to Carl Orff’s O Fortuna, Carmina Barana for twenty four hours while drinking lukewarm, creamerless coffee and staring at your own reflection. In any case, it’s not good to brag about which method of distorting God’s immutable Law you favor in your literature. That tends to lead to mistunderstandings and the odd Inquisition, the first of which is awkward and the latter of which is excruciating. The important thing to keep in mind here is that there are a few core reasons for creating an anthropomorphic character, and if you ignore them, you might be better off just throwing in that talking cat. As long as you’re writing fantasy or a space opera involving hand-flaily genetics jargon, no one is going to call it into question. I mean, damn, talking cats are everywhere. Isn’t it odd we don’t have quite as many talking dogs? Or at least, I feel like we don’t. Maybe it’s because real dogs never seem to shut up.
First reason for anthropomorphs- recognizable facial expressions. These are absolutely key, and they are absolutely key because this is the single biggest advantage to creating an anthropomorph. Humans have all sorts of body language, and a lot of it doesn’t translate well from one culture to the next; facial expressions are the big exception. A happy man from the United States would still appear happy to locals in Tokyo, Paris, Johannesburg- you name it it, doesn’t matter, a smile is a frigga-fragging smile. Sword-wielding feudal maniacs had pretty much the same sets of warfaces no matter which country you look at, and most countries are equally glad to have them gone. If you want to have a non-human character with human appeal- which is generally all the more critical in the sort of stories that feature non-humans- making sure they can still use our same set of expressions is pretty useful.
Secondly, examining common thought processes and societal biases through the lens of a character who would not, inherently, have accepted them. Whatever you do, don’t write a fantasy novel just to preach to people, but in any longer work a number of issues can and often will come up, and when they do it’s good to have someone on hand to address them who people are, in a way, expecting to do so. A human picking on issues in human society is going to seem too on the nose (perhaps an unfortunate choice of phrase, that close to the verb ‘picking); by throwing in somebody who sort of looks human(ish), but is obviously totally different from a human except for having the ability to hear and reproduce our full range of speech, you can still feed your inner social activist while simultaneously making your readers think you’re deeply philosophical. I’m not kidding. Lines that no one would take seriously coming from a human character will strike them as the best [YOUR EXPLETIVE HERE] ever if you just have a giant snake with arms say the lines instead. In fact, this is the preferred method for over 90% of high fantasy writers. The remainder are either Tolkien or the people who want to write fantasy without writing anything that sounds too much like fantasy.
And lastly, because an anthropomorphic character is not fully human in form, you can have them do things that a human would never be capable of, but they may not be able to do some things you or I would consider trivial. This is something you’ll really want to think carefully about, because, let’s be honest, how would something with no legs jump? Jumping is a motion made possible by the diversion of all the muscle power on a rigid structure (the leg) down through a supporting structure (the foot) so that both structures and the structures above them make it a few feet off the ground (useless). And don’t mention fish, because they’re underwater, and that means that the same amount of force will carry them much further. Cars can’t jump without ramps. These things don’t so much jump as launch themselves. It’s the same group of principles as applied to missiles. And missiles don’t jump. That’s the sort of thing that would make for very awkward press conferences.
Just please stop taking woodland animal heads and grafting them on to furry but otherwise humanoid bodies. That’s simultaneously really weird and really lazy. You’re better than that! Also, the Redwall books did it better.