One of my cats sleeps in a plastic bag, he was a rescue cat and I'm thinking it was probably something to do with that. The other cats love to kill plastic bags - so you can imagine what can happen sometimes when they don't realise Sqiggles is in in the bag. (Squiggles as he had a broken pelvis that wasn't reset and so his back legs aren't aligned so he's a little squiggly when you look at him). My old cat will chew bottle tops if they're still on the bottle, I haven't figured out why yet. My female cat will chew a nail file if she can get hold of one, she'll spend a good hour trying to pick it up with her claws and pop it into her mouth with her paws (should try to get it on camera), she also shreds my bin liners, the part that goes over the edge of the bin, but only when it's a new packet of liners, once they've lost the smell of new liners she doesn't bother. Rolled up tin foil balls, and crisp packets are good fun to chase and kill too.