My now-deceased cat used to answer the phone. I had an older, "cradle" style phone, and when it rang she would pull it off the hook and just meow at it. Drove people crazy, because they couldn't leave a message and when they called back the phone would stay busy all day until I got home. She also would turn on the water in the bathroom sink to get a drink, so I had to be sure never to leave a stopper in the drain.
A friend of the family had a cat who was very self-sufficient. He could unlock the front door to let himself out, but of course could not lock the door behind him. He also fed himself, which led to a very funny incident one night. His owner left Tender Vittles packets for him in the kitchen cabinet, and he would just open the cabinet and grab a pack when he felt hungry. Then he always took the packet into the bathtub to eat it, which was actually pretty considerate. This went fine for years until one day someone unfamiliar with the routine helped his owner put away the groceries. In the wee hours of the morning he went to get his packet as usual, took it into the bathroom, tore it open and dug in, and then started howling fit to wake the dead. The problem: he was eating a packet of Lipton Onion Soup mix!