SpongeBob is not your friend.

That is the message of a lawsuit announced yesterday, asserting that characters like SpongeBob SquarePants - despite his ever-present grin - are harming children's health by hawking what the plaintiffs' consider to be junk food.

The Center for Science in the Public Interest, the Boston-based group Campaign for a Commercial-Free Childhood and two parents served notice that they intended to sue Viacom, the maker of the popular children's TV show "SpongeBob SquarePants," and the Kellogg Company, a big marketer of food to children, which features the lovable SpongeBob on packages of cereal, Pop Tarts and cookies.