There's a twist in "Iron Man 3" that can't be discussed directly because it would spoil a major plot turn about a decades-old character. Let's just say that it surprises longtime fans of the franchise's heroes and villains — at least the comic-book version.

But the twist, shocking as it is, is no big deal in the scheme of things. The first victim of the rush to put characters many of us have known for decades on the big screen is fidelity to decades' worth of comic-book mythology.

Everything about well-known characters, from the way they look on the original comics page to how they interact with other iconic characters, will have to be updated and translated so that movie audiences aren't left in too much of a psychic lurch.

For instance, movie audiences watching the upcoming "Man of Steel" won't have to wonder why Superman, Earth's immeasurably powerful alien savior, would subject himself to world ridicule by wearing red underwear on the outside of light-blue long johns. After nearly 80 years, even the most orthodox of comic-book fans has had enough of that silliness.

Superman's wardrobe, along with the Boy Scoutlike demeanor that has been a key part of his appeal in comics and on the screen, gives way to the needs of a contemporary audience that prefers modern heroes with a large heaping of angst on the side.

Characters conceived in the Depression-scarred imaginations of young men (Superman, Batman), the fires of World War II (Captain America), the Cold War just as the counterculture was heating up (the Marvel Comics revolution of the 1960s) would be unintelligible to modern audiences without major revisions.

Michael Keaton made the Batman role his own.

The psychological insight of director Christopher Nolan's take on Batman in his mostly excellent "Dark Knight" trilogy has become the gold standard for exploring the inner lives of these comic-book archetypes.

Nolan's skill as a translator of comic-book mythology to the big screen made it possible for less-skilled directors to get the benefit of the doubt from the easily caricatured "fanboys" who used to nitpick everything.

Remember when the casting of Michael Keaton in the pre-Nolan incarnation of Batman generated howls of outrage in comic-book shops across America? Those early boos quickly turned to cheers after the Pittsburgh native made the role his own despite not looking anything like the fans' ideal version of Bruce Wayne.

When Tobey Maguire's version of Spider-Man shot organic webs from his palms instead of from mechanical web-shooters, there was some initial grumbling, but that quickly faded because of the sheer fun and spectacle the movie provided. The original "Spider-Man" movie did so many things right by new and longtime fans that to hold a grudge over the nature of web-shooters would've been churlish.

Still, I'll admit to having once been a major skeptic about the casting of Robert Downey Jr. in what has become his most iconic role. I was won over by his brilliant portrayal of Iron Man's alter ego, not by the billions his portrayal generated worldwide.

Before Downey, Tony Stark had been portrayed in the comics as a suave billionaire industrialist who was emotionally distant until recurring bouts with alcohol humbled him.

Stark was rich but never vulgar. He was a repentant munitions maker and Cold War playboy on the hunt for deeper meaning in life.

Up-ended expectations

Despite his flaws, he took life and his role in the superhero pantheon seriously. If the character had to make the jump to the big screen, it seemed like a role the effortlessly charismatic George Clooney was born to play despite his disastrous turn as Batman/Bruce Wayne in the late '90s.

What Downey did was turn our expectation of Tony Stark on its head. Instead of a tall, lanky, elegantly attired and self-consciously sober businessman who just happened to exude irresistible charm, we got an impulsive, quip-generating, capitalist wise guy whose inability to pick up on social cues reminded us of our buddy with Asperger's.

The novelty of Downey's performance breathed a much-needed spark into the trilogy's first installment. That spark became an annoying tic in "Iron Man 2," which was almost universally panned as a misuse of all the actors involved.

Downey's performance as Iron Man in "The Avengers" was balanced by strong performances by lesser-known actors in iconic superhero roles. Meanwhile, the influence of Downey's portrayal as Tony Stark/Iron Man can be seen in the comic books, where a weird role reversal has taken place.

The comic-book version of Tony Stark now physically resembles the actor who plays him. Suddenly, Stark makes just as many quips as Spider-Man and could be categorized as aggressively shallow by superhero standards most of the time.

This is, no doubt, an attempt at corporate synergy on the part of Marvel Entertainment, but if Downey was of a mind to bite the hand that has fed him so well, he could conceivably sue Marvel for royalties. The character in the comic book is clearly crafted in his image now.

Now that "Iron Man 3" is in theaters, there will be debates among comic aficionados about what director Shane Black got right and wrong about the characters and the Marvel universe. Certainly the absence of a certain espionage group from the film is glaring and will be much commented on.

There are other gaps in the film's logic that you'd never see in any self-respecting comic book, but the superhero-movie universe is a weird place. Superhero movies are more grounded in reality but less grounded in solid storytelling than the comics that inspired them.

Movie directors have found that they can get away with a whole lot more than their comic-book counterparts. They don't have to worry about the squeamishness of fans caught up in the cult of comic-book continuity. Movie directors bringing comic-book mythology to the big screen aren't oppressed by the burden of representation at all. For them, the bottom line is always the bottom line. Even the mightiest of heroes must yield to that.