Dude adores Primark bags. He gets a bit possessive over them too - if you touch it, you WILL be clawed at. All of mine LOVE cardboard boxes, and anything box shaped. If something is left on the floor, there will be a cat (or 3) in it. Dude hates tinfoil, its the only way to keep him off the Christmas tree, but the other two love tinfoil.
They all go crazy for carrier bags, but thankfully don't eat them, and so far we have found out that Dude likes donner meat, Chester likes Wotsits, and Gordon loves ice lollies. The two little ones don't quite understand windows yet, so will spend endless amounts of time pawing at rain, and making a strange clicky meow noise at the birds outside. Dude has learned to climb up our 3 storey house, and is often at the velux in the attic room, meowing to get in like its some kinda amazing huge catflap. I've already had the neighbours down the way complain about him, as apparently he quite likes their window too......
And so far, I STILL have two Christmas trees intact. Granted, there are no decorations on the bottom 3rd for a reason, but at least they are still vertical!