Hi, I'm new here (so please be nice)
One of mine (I couldn't put their pictures in a signature, but I currently have three four legged tyrants) demands food, and if he doesn't get it immediately (for example if it's about 4 hours too early), he stomps off and searches for plastic to eat just out of my reach, glaring at me as he does so. He knows it's bad, but does it purely out of spite. I'm practically neurotic about kids leaving any plastic around because of this. No real medical cause, just him being a pain and knowing it will get me launching out of my seat to catch him!
Worms never really bothered me. Cats get fleas, cats get worms: it's something that animals do. But then again, I was pretty much feral as a child, spent more time on the floor with the animals than up with humans. If I could persuade my mother to get the cats some medicine, I would give it to them. But then, she never hoovered upstairs, so it was probably pointless anyway. I dread to think what nasties I caught over the course of my childhood!