Another sign that we'll never again see children's entertainment that actually places entertaining children first: Cookie Monster is shilling for moderation in eating cookies. Wile E. Coyote wouldn't even get on the air today. "Sesame Street" has always been both educational and moralistic, and that's a good thing. But Jim Henson understood that a little plain old childish mischief is what made the show work well enough to keep kids coming back for more letters and numbers.