Cartoonist Robert Crumb is the father of the underground comix movement of the 1960s. Born on August 30, 1943, Crumb's first job was drawing greeting cards. He grew tired of the gig but for a long time wasn't successful selling his cartoons to comic book companies.

Crumb's first successful character was created in 1959. Fritz the Cat was a horny, self-centered cat. The comic was adapted into a hit movie by Ralph Bakshi in 1972 and became the first animated feature film to be rated X in the US. Crumb didn't like the film project and published a story in which Fritz was murdered by an ex-girlfriend that same year.

Crumb took a lot of LSD and the drug inspired his comics. Introduced in 1967, Mr. Natural became Crumb's most famous character, with his image appearing on different merchandising products. A mystic guru/charlatan who likes to share his cosmic insight on the evils of the modern world, Mr. Natural is moody, cynical and has various strange sexual obsessions.

Introduced in 1967, Whiteman symbolized the repressed big-city businessman, always on the verge of a nervous breakdown and constipated. But Crumb didn't promote a progressive and idealistic anti-capitalist worldview. He was purely transgressive. His work was provocatively filled with demeaning depictions of women and ethnic minorities, to put it mildly.

The character above is Cheryl Borck, aka Devil Girl; she had a tempestuous affair with Mr. Natural. Incest, necrophilia, scatology, assault: The cartoonist was never afraid to reveal his erotic fantasies and sexual obsessions in his work, breaking taboos and crossing lines that would certainly bar him from any form of mainstream success today.

The one-page comic strip "Keep on Truckin'" was published in the first issue of Zap Comix in 1968. The three simple words of encouragement became extremely popular among hippies and the strip, an icon of optimism. Instead of enjoying the popularity, Crumb later described the cartoon as "the curse of my life," because "I didn't want to turn into a greeting card artist for the counter-culture!"