If I close my bedroom door at night, Pepper will knock on the door to let me know that he wants in or out. All 3 of them will also push on a closed door to try to open it up. They also open up cupboard doors to bat at them and play with them. If I have my sliding glass door open, Storm can open the screen door. He'll then go out on the balcony and Pepper and Sunny will follow him. This has become a real problem so I keep a spray bottle close by so that when I see him doing this I can spray him. Now if I show him the bottle he'll run.