If your local mailbox is looking suspiciously like SpongeBob SquarePants, you haven't sipped too much eggnog. It's a nationwide campaign to encourage kids to write letters and postcards during this holiday season. Children can get a freebie postcard at their local post office to send off a missive to a friend or family member. They have until Jan. 4 to take part in this letter-writing campaign. And some 30 mailboxes around the country will be adorned in SpongeBob's SquarePants to call attention to the event.