Ok, so after playing around with my graphics settings;
the Cat is fine in-game. On the loading screen, or in Create-A-Pet, it is deformed, as well as having its head deformed when it is the active sim.
I can live with that, it's just annoying. Functionally, it just means that I can't change the coat colours.
However, if I get daring, I'll do a complete uninstall/reinstall tomorrow; since I did install Pets over a game that's patched to 1.33, so that could be the source of my problem.
Edit: After scouring the internet, I feel like an -idiot-. I have a mod that may be the source of the problem (it's the one that has the toddlers standing in CAS). This is what I get for installing/playing while tired. Wow. So I'll see if a mod is the culprit.
Edit #2 Yep. I just did a test run without anything installed, and it works fine. *sigh* I got over-excited, thinking that since all my mods were patched up and everything ran fine. . . . It's my own stupid fault. Now to make sure it's just the one mod in question.