Characters Who Originated on Greeting Cards

When we think about places where multi-media characters started out, very few of us think of greeting cards. Yet, some major properties (and other minor ones) started out as greeting card characters. Tom Wilson, Robert Crumb, William Steig, and more drew greeting cards for companies like American Greetings, Hallmark, Shoebox, Box Cards, Bop Cards and more.
I didn't include My Pet Monster or Mad Balls which started as toys made by American Greetings, not as cards.