Do they know what they are? Did they try to sneak into them before you put them up? My Noah tries to do that.
This year I got a little smarter, last year I bought the presents first then the stockings. Trying to hide a bag full of kitty goodies was a difficult task. Everyday I would have a new hiding spot and everynight Corkscrew would find them. This year when I brought out the stockings Corkscrew quickly got bored after he stuck his head inside and found that it was empty. But as soon as I get my next paycheck they will be full with lots of goodies .