(CNN) "Batman" swooped into theaters on June 19, 1989, helping set the stage for more blockbuster superhero movies as well as more adult, ambitious takes on the comic-book fare that, this century, has become the dominant movie genre in box-office terms.

The run-up to the Dark Knight, however, also underscored a darker side of fandom, one that seems to become uniquely passionate -- and in some quadrants, enraged -- when it comes to casting actors to play Gotham's hero, from Michael Keaton to Ben Affleck to, now, Robert Pattinson.

Twitter didn't exist when Keaton landed the role, but if it had, the entire Internet might have overloaded. Many longtime readers of the comics (including this one) wondered how director Tim Burton could tap a comedic actor, his "Beetlejuice" star, to play a character with the mind of Sherlock Holmes, the physical prowess of James Bond and the nasty streak of Dirty Harry.

Still, the "Batman" that emerged became a huge success, perhaps as much in spite of Keaton as because of him. He was fine, but it was everything else -- Jack Nicholson's loopy but menacing Joker, Danny Elfman's sensational score, a way-cool new Batmobile, and a general look that resembled the work of comic-book artists Neal Adams, Marshall Rogers and Frank Miller -- that defined this Batman, and separated him from the "Wham! Biff! Pow!" camp of the 1960s TV show starring Adam West.

Michael Keaton portrayed Batman in the 1989 film 'Batman' and the sequel, 'Batman Returns' in 1992

The good news, alas, didn't last, as the movies became increasingly campy, with first Val Kilmer and then George Clooney taking turns under the cowl.

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