There's little doubt Watchmen changed the comic book landscape forever. The seminal comic book, by Alan Moore and Dave Gibbons, raised the bar on superhero stories by both deconstructing and recreating superheroes with a flawed yet human outlook. But while characters like Rorschach and Dr. Manhattan might seem like iconic masterpieces, they all have their roots in one place - Charlton Comics.
While Watchmen's world of superheroes gone awry is buzzing with originality, Moore himself originally planned to use characters from Charlton Comics to form the core cast of the book's central murder mystery. He submitted a proposal, centering around the death of the Charlton character Peacemaker, to DC Comics executive editor Dick Giordano, who subsequently convinced Moore to use original characters instead of their Charlton counterparts. Thus, the world of Watchmen was born.
Charlton Comics originally started as the T.W.O Charles Company in 1940 before rebranding itself as Charlton Publications in 1945. Like many publishers at the time, they produced comics in a variety of genres, including superheroes, suspense, and horror. The company's most recognizable creation, however, would appear during the Silver Age and would include such characters as Captain Atom, Blue Beetle and the Question. These characters were later acquired in 1983 by DC Comics.
Thus, much of the cast of Watchmen have their origins in Charlton Comics. The Comedian, whose murder kicks off the events of the DC maxiseries, is based on the Silver Age Peacemaker, who ironically uses a vast array of non-lethal weapons, unlike his violent Watchmen counterpart. Nite Owl is based on the Blue Beetle, with both characters presented as legacy heroes taking the mantle from a predecessor. Silk Spectre is based on Nightshade, though she also shares some similarities to another DC character - Black Canary - who like Blue Beetle, is a legacy character. Doctor Manhattan is based on the nuclear-powered hero Captain Atom, though the latter never displays the reality-altering abilities of his Watchmen counterpart, who likely also shares some similarities to near-omnipotent characters like the Spectre. The mastermind of the piece, Ozymandias, is based on Peter Cannon, Thunderbolt, who literally has "mind over matter" as a superpower. Finally, the troubled anti-hero Rorschach is based on the Question, the objectivist hero created by the legendary Steve Ditko.
This does raise the question - what would have happened to these characters if they were originally used as intended in Alan Moore's Watchmen. The story ends with New York City vaporized from a fake alien invasion perpetrated by Ozymandias, Silk Spectre and Nite Owl retired with new identities and Rorschach killed to the secret of the plot hidden from the public. This would have spelled a very different ending for the Question, who went on to appear in a 1987 solo series by Dennis O'Neil and Denys Cowan, where the character developed a notably more Zen-like quality. The Question would go onto mentor heroes like the Huntress before eventually perishing from cancer and passing on his mantle to GCPD detective Renee Montoya, though the original Vic Sage version has appeared from time to time after The New 52. Similarly, the Nightshade of DC Comics bears very little in common with Silk Spectre, appearing as a Suicide Squad operative and Shadowpact member. Similarly, Blue Beetle would have likely never developed into the best friend of time-traveler Booster Gold had his character appeared as planned in Watchmen.
Regardless, it seems unlikely the Charlton characters would have developed the same way if there were re-introduced in Moore's seminal comic book. The decision by Giordano to use original characters arguably proved best for both characters, giving Moore's project the chance to forge its own path while the newly-acquired Charlton heroes developed organically in the decades following. While Doomsday Clock has brought characters like Dr. Manhattan and Rorshach back into the limelight, the Charlton characters have, like their Watchmen counterparts, taken a completely different life of their own.