I take cold showers. I soak in hot tubs. I jog""--but Waber's harried, bedeviled cat can't get mice off his mind. He tries to entice them into his home, hut to no avail; he pours out his obsessive fantasy to a shrink, only to find that the psychiatrist has the same problem. One fixed thought, one character, no development--even if you don't make the obvious three-letter substitute for the word mice you can still wonder how much of this is aimed at kids. (""I give at the office,"" says Mr. Cat, while listing his virtues.) And if you do, Waber still doesn't take you anywhere. As pictured, though, his feline gentleman puts on a one-cat performance that might trap any audience.