Modesty Blaise was a comic strip character that was adapted into novels, not a paperback original character, so I'm a little unclear on the subject heading.

Michael Chabon's The Escapist is a (Pulitzer Prize winning) 'paperback original character' who was later adapted to comic books.

Zorro, Charlie Chan, Sherlock Holmes, James Bond, Dracula, Frankenstein and Fu Manchu were all literary characters that were later adapted to comic books and/or strips.

What was the question again?