SillyRed, this is what happens: A boy and a girl are fighting over who gets a cookie. Cookie Monster stops by and offers to help them solve this problem: he decides that the smallest one will get the cookie. Needless to say, the kids start arguing about who's smaller. Then - this is the freaky part - Cookie Monster literally
shrinks himself (just by standing still
) and the kids are astonished. Cookie remarks,
"Me do anything for cookie!" and walks off carrying the giant cookie in his mouth.
Is this the one you're thinking of?