I think you mentioned something about them not being able to have 2 cats because of their lease, but your dad didn't care. Maybe the cat needs a friend if your parents cant play with him enough. As a kid, I had a cat that would attack my ankles - I don't think he was playing and I probably instigated it!!! Last year we got a kitten to replace our cat that had passed away - the other cat needed a companion. Ringo is full of energy. I kinda feel bad for the other cat, as he chases her around (but she ate for comfort after Hershey passed, so she needed to lose weight anyhow). Fortunately, we have a golden retriever who is Ringo's BFF. They love each other, run around the house, wrestle, and play a lot. I imagine if we didn't have the other pets to occupy him, he would probably want quite a bit more of attention from us, and I don't know that we could keep up with him!

I also keep a lot of toys out for all of them to play with, and he's a real toy lover. His interest in toys has lulled a bit since he was a little kitten (he's almost a year now), but he does play. His favorite items are socks, and he steals any of our socks he can get. DH isn't the best at putting his laundry away, or just cramming it into the drawers so they dont close all the way - Ringo will sit on the dresser and reach down into there and jank the socks out of the drawer! Just like with our dog, I try to get them new toys every month to stimulate their pet brains and occupy their time. DH found these "cat condos" at the pet store - you can buy them in sections and build it as big as you want. Ringo loves his little home - it has scratching posts on it, little "rooms", a hammock type top that he lounges in. He and the other cat play hide and seek in it. I guess what Im getting at is just try to keep him busy. It's like a hyper child, and his attention needs to be redirected. Sounds like he really likes your dad, and that's why he engages him. I also second the spray bottle when he's doing something he shouldn't be, but it should be used without any sort of verbal que so he doesn't associate it with your folks, rather with the activity it self. Ringo is too damn smart, and knows we work the spray bottle. All we have to do is pick it up and he stops what he's doing - doesn't do much good, though, as he knows when we're gone he can do whatever he wants!!
Good luck!