There's a strong probability that the whole idea of cow tipping, rural kids sneaking up on sleeping cows to tip them over for fun, is a myth, even impossible as a matter of physics. But for some reason, it is the prevalent movie theme of 2006, at least in movies for kids. We've already seen cow tipping jokes in "The Wild," "Cars," "Barnyard," and this week "Zoom." Hey, it wasn't funny the first time. Or the second, third, or fourth. Let's put that joke out to pasture.