Is it the feline equivalent of Alzheimers? Or some viral infection? My understanding's that it's deadly. I don't want to overreact,but Percy's behavior is changing. He's doing stuff he never did before, like digging in the garbage. He keeps demanding I feed him-when he's already eaten plenty. He's cranky. This is not my Percy-fruit!
If it's any comfort, Nito digs in the garbage, demands food, and has cranky spells every day and he's been given a clean bill of health. Either way, if you've noticed a drastic change, a checkup never hurt anyone.
Mostly you can always look something like this up on the Web. (I just typed 'distemper' into Microsoft's Bing search engine and went on from there.) What you describe doesn't sound like the description of feline distemper given here. http://en.wikipedia.org/wiki/Feline_Panleukopenia
Tapeworms, an intestinal parasite, can make a cat grumpy and would also make them feel hungry all the time. A vet visit is definitely in order.
Tapeworm is not a dire problem, but you should bring Percy to see his doctor.