Personalities would be hard, well, unless I made different behaviour patterns eg; lazy not moving much, hyper moving more than usual, etc.
There should be a set of variables one through ten that change by how you treat it. For instance: If you praise it allot, it won't think as much of praises, but be affected allot by scoldings, or if you scold it allot, it will be the reverse, and if you do it evenly, they will effect it evenly. Another example is if you feed it allot then it will grow to expect food the moment it asks for it. If you give me a list of things you can do, I can give a list of personality traits they can gain.
This would make it so instead of them just doing random stuff, they gain personalities that you can talk about. So you can say yours is a wimp, a spoiled brat, or a hyper freak. By having just a few trait variables, you can have hundreds of combinations.
