Back in the day when comic book companies had yet to be taken over by the big two there was Charlton Comics which gave birth to some of the greatest characters in the entire comic genre. The characters were absorbed by DC and largely written out of the DC Universe during Crisis On Infinite Earths in 1985. Watchmen writer Alan Moore originally wanted to use these characters in the Watchmen but DC persuaded him to create new ones which he did. Here are the characters the Watchmen were based on.
Here are the Watchmen as we know them. Top to Bottom: Dr. Manhattan, The Comedian, Nightowl, Ozymandias, Silk Specter, Rorschach.
Here are the characters they were based on:
CHARACTER: THE QUESTION
BASIS FOR: RORSCHACH
Victor Sage was a TV Journalist hellbent on Justice. When he discovered how to use a technique that allowed him to have no face or the face of others he became The Question a vigilante on the same page as Batman. Not nearly as psychopathic as Rorschach nor as violent. Had more of a detective angle than just brute force.
BASIS FOR: OZYMANDIAS
Peter Canon was an orphan raised in a Himalayan lamasary after his medical team parents died battling the Black Plague. Training himself Canon achieved peak physical and mental perfection and was then entrusted with the ancient scrolls that awakened unused portions of his brain making him nearly superhuman. Though he shares the same looks and physical abilities as Ozymandias, Alan Moore took the generous spirit and self-sacrificing nature of Thudnerbolt and totally reversed it for his character.
BASIS FOR: THE COMEDIAN
Christopher Smith was the son of Nazi soldiers, a fact that haunted him his entire life. Smith become dedicated to vengeance on all levels against anyone he thought was doing the wrong thing. Though similar to Rorschach Peacemaker's sarcastic wit and deep belief that everything was tainted and awful so why try to be better made him the jumping off point for the morally bankrupt Comedian.
BASIS FOR: SILK SPECTRE
Eve Eden had a normal mother but a father who was an interdemensional being thus giving her strange powers to travel in and out of other dimensions. Nightshade's look and dislike of being a superhero plus the estranged relationship with her father played heavily into the design of Silk Specter for the Watchmen. Clearly Moore's ideas are further developed and mature but you can see definite similarities here outside of them both being female.
CHARACTER: CAPTAIN ATOM
BASIS FOR: DR. MANHATTAN
Captain Allen Adam was caught in an atomic accident and from that became the "Superman" of Charlton Comics. Invulnerable, able to fly at super speeds, incredibly strong, etc. Moore used the idea of this hero being taken from the Atomic Age and gave him much more depth and a more god-like ideal even changing the look completely. Though Captain Atom has remained in the DC Universe (though in radically different ways) it was this original idea that inspired Moore.
CHARACTER: THE BLUE BEETLE
BASIS FOR: NIGHTOWL
Dan Garrett was an archaeologist given superpowers through a scarab he found while on a dig. Though the look of this original Blue Beetle served as Moore's basis for Nightowl's look, it was the second version of the Blue Beetle, one that had the hero using science and technology, that was used for the character itself.
So that's the deal with The Watchmen, pretty awesome I think.