I think this is the right track, but perhaps not intro/extro, and simply what people want from a pet. Want a constant companion? Get a dog. Want another thing s

I think this is the right track, but perhaps not intro/extro, and simply what people want from a pet. Want a constant companion? Get a dog. Want another thing sharing the space, that can look after itself? Get a cat. Want something pretty to look at that knows it's place? Get a fish...