Things that have sparked their curiousity- the fish tank. Zakk used to like the toilet, and still has a fascination with the shower. He is also very interested in the litter boxes getting cleaned. Rocky used to think that the mouse on the computer was neat. Zakk also is fascinated with exploring high spaces that he usually can't get to- like cupboards, closet shelves, that kinda thing.
Cookie is the only one who ever seemed interested in TV- he stood on his hind legs one day and just stared. Suzy seems interested in watching what we humans do, but not getting to close.
Oh yes, and we have a sump pump in the basement. Zakk hasn't figured out what the heck it is down there yet that makes those water and groaning noises.