Can animals laugh?

"Laughing" in this case need not be defined as the vocal thing that humans do when they find something funny. It is better defined as a state in the brain that provokes a reaction in animals, whatever that might be, that appears to be identical (in the brain) to what is going on in a human's head when they "laugh". So if you are waiting for your cat or dog to start hee-hawwing like a person you're in for a long wait. That doesn't mean that they don't "laugh" though, they just do it in a way that you don't recognize.

As for animals having personalities, I definitely agree. I had several cats (and a dog or two) growing up and they all had their own personalities despite being treated the same as kittens. One of our cats was real aloof, his cousin however was very needy and affectionate. One cat was the dominant leader of any animal that came into the house (except our Iguana) and was also very modest. He'd play with kitty toys and things... but not if he thought he was alone!