In
Peanuts, a characteristic that
Frieda (sometimes seen spelled
Freda but it's Frieda in the strip where
Linus introduces her to
Charlie Brown) constantly
brags about. Her first words to Charlie Brown are "How do you do, Charlie Brown? I have
naturally
curly hair!"
And, of course, from A Charlie Brown Christmas when the children are being assigned parts in the Christmas play:
"Do innkeepers' wives have naturally curly hair?"