Teaching an Old Cat New Tricks

My wife and I have a eight-year-old cat named Phoebus, whom she rescued as a kitten. When she found him, he was one week away from being put to sleep by the local shelter; his mother had leukemia, and of his entire litter, only he had survived. He's a great cat, with a firm but sweet disposition, and, until recently, he had never been clicker trained. He did all the normal things you want a cat to do—use a litter box, hunt mice, play, purr—but he also did some of the normal things you don't want a cat to do.