The cats long ago figured out how to open the hall closet. It's got the sort of door latches that don't turn; you just pull hard enough on them and the doors part. This unnerved me when I first saw my parents' house because I expect those doors to work like normal doors, and like nearly every other door in the house. Anyway, since the cats can't open the doors by pulling on the handles, for sound reasons of non-cartoon leverage (although they'd be able to manage it if they pulled on one handle while hanging diagonally to set their hind feet on the other), they have worked out an alternative.
They start out by scrunching up on the floor, and putting a paw underneath the door. Then they tug. It's just a little tug, but they keep at it as the door rocks back into place. And tug again. They do manage if they keep at it to make one of the doors swing open, allowing them to hop into the closet and remember that there isn't anything that interests them in it. You may smile amused at them for taking so long as they do since they don't tug the door in synch with its natural vibrations. But I can't say that the cats' understanding of resonance modes is actually any worse than the understanding students in Introduction To Differential Equations 2400 have.
The study has a similar set of doors with non-swinging latches, but since these doors open into the study rather than out into the hall they can't get the leverage by putting paws underneath the doors. But they seem to have cracked this problem too, and in the past few days because I see them in the joy of having figured how to access a room previously closed off.
Their approach is to run from across the living room and leap into the door, hitting it broadside until the force rocks the door open.
I hope they're proud of themselves, since now the only doors they have left to figure out are the normal bedroom swinging-latch doors. After that they'll have nothing else to solve. Also I fear what'll happen when they discover my father's put the Cuisinart bread maker behind one door.
Trivia: The Roman Emperor Commodius tried to rename the second month of the year `Invictus', after one of his many names. Source: Mapping Time: The Calendar and its History, EG Richards.
Currently Reading: Superdove: How The Pigeon Took Manhattan ... And The World, Courtney Humphries.