No, I don’t mean like Kananga in the movie version of Live and Let Die, or Violet Beauregarde in Willy Wonka. I mean “inflated” in that their role and importance was increased by later writers and contributors to a character’s adventures by people other than the creator. Evidently the folks responsible for churning out a series of books or movies or comics feel that the hero should have one significant adversary people can easily identify. So they end up being inserted into stories where they didn’t originally appear, and the show up more frequently in pastiches.
Professor Moriarty – Sherlock Holmes’ nemesis, who was responsible for Holmes’ death (and his own) in the short story The Final Problem. After Doyle was virtually forced to revive Holmes, Moriarty showed up again in the novel The Valley of Fear, but I can’t reconcile the two. He’s mentioned in a few other stories, but Doyle never re-used him. William Gillette made him the main villain in his stage play sherlock Holmes, but that’s understandable and perfectly kosher – he was adapting few Holmes stories, including The Final Problem. But universal made him the villain in their second Holmes movie, The Adventures of Sherlock Holmes. And Dennis la Rosa had him as the power behind the robberies in his stage adaptation of The Sign of Four. John Hawkesworth made him the power behind John Clay in the Granada/PBS version of The Red Headed League. And he’s in the TV movie Sherlock Holmes in New York. John Gardner and Anthony Horowitz have written entire novels centered on him. He’s in Alan Moore’s original League of Extraordinary Gentlemen. And in Nicholas Meyer’s The Seven per cent Solution. And tons of other pastiches.
Ernst Stavro Blofeld – James Bond, in Fleming’s novels, is really fighting against the Soviet Union in most of his novels, but he created the international criminal syndicate S.P.E.C.T.R.E. for Thunderball (in collaboration with Jack Whittingham, Kevin McClory, and others. I suspect they’re responsible for swaying Fleming away from Russian Bad Guys. Heck, even Goldfinger, in the novel, was a Russian paymaster, not an independent as in the movie), and that organization needed a leader. This, Ernst Stavro Blofeld, who only appears in three Fleming novels – Thunderball, On Her Majesty’s Secret Service, and You Only Live Twice.)
But he’s the Bad Guy in eight of the Eon films, as well as in Never say Never Again. But he also appears in video games and comic book original stories. Curiously, he’s not in any Bond novels written by people other than Fleming. Maybe they wanted to avoid the legal complications that held up his use in other films (He’s not named in the opening sequence of For Your Eyes Only, although it’s clearly him. And the villain in the film The Spy Who Loved Me was supposed to be Blofeld, only there were legal disputes over use of the name.)
Thoth-Amon – Conan the Barbarian didn’t need a recurring villain. The Stygian wizard Thoth-Amon is mentioned in only three Conan stories written by Robert E. Howard, and the two never meet in his works. But editor L. Sprague deCamp wanted an adversary for Conan, so he added him in the story The Black Stranger that Howard wrote (and which deCamp changed the title of, to The Treasure of Tranicos) and added him to the pastiches he and Lin Carter wrote. Robert Jordan and others used him, too. When Marvel comics started adapting Conan, Roy Thomas followed deCamp’s lead and added Thoth-Amon as a significant opponent in the comics. Dark Horse comics did this, too.
Any other cases out there?