Conversation so far:
What is Zap Comix?
Zap Comix is an underground comix series which was originally part of the youth counterculture of the late 1960s.
How was the response to Robert Crumb's work for Zap Comix?
Crumb had difficulty at first finding retailers who would stock it, and at first his wife took to selling the first run herself out of a baby carriage.
What more is known about Robert Crumb and the underground comix?
How did Robert Crumb's sexually explicit work do?

Question: What were these best known works?
Self-contained rewrite: What were Robert Crumbs best known works?