Jim Carrey entertains himself mightily, and his enthusiasm is infectious. He plays Fletcher Reede, an unscrupulous attorney whose son makes a wish that Dad stop lying for 24 hours. The wish comes true. Suddenly, Fletcher can’t lie — he becomes incapable of spitting out anything but the truth, no matter how rude or embarrassing. Carrey, tying his face in knots, is like a man in a straitjacket: The more he tries to lie, the harder the truth straps him in. The story is straight out of a Chevy Chase movie, but Liar Liar isn’t a ”family” comedy or even a real satire. Its central relationship is the one between Jim Carrey and himself. B