Alfred E. Neuman first appeared in American iconography decades before his association with Mad. It is believed that he first appeared in an early twentieth-century advertisement for painless dentistry. Hence the missing tooth and the motto "Me Worry?"
By unknown (not relevant to copyright status) - Image from http://community.webshots.com/photo/304039856/304041768aZxySa# (Webshots), Public Domain, https://commons.wikimedia.org/w/index.php?curid=2444772