By Jill Lawless

VENICE, Italy (AP) --

Well before the turn of the millennium, Michael Keaton was the first 21st-century superhero.

Keaton's role as Batman in two Tim Burton-directed blockbusters a quarter of a century ago made him a global star, and helped spawn a Hollywood obsession with comic-book franchises that has put a generation of leading men into spandex.

Whether that was good for the movies, or the stars, is at the heart of Alejandro Gonzalez Inarritu's "Birdman or (The Unexpected Virtue of Ignorance)," which opened the 71st Venice Film Festival on Wednesday.

The soul-searching supernatural comedy-drama stars Keaton as Riggan Thomson, an over-the-hill actor, once famous as avian superhero Birdman, struggling to regain his self-worth by mounting a heavyweight Broadway play.

So how much Michael Keaton is there in Thomson?

"That's the giant elephant in the room," the actor conceded in a Venice press conference. But, he added, he'd recently been to Africa and was very fond of elephants.

Keaton, 62, insisted he's happy with his place in movie history, but said the credit for reshaping superhero movies should go to Burton.

"It's been copied, sliced up, what Tim did — more than cocaine from a cartel," Keaton said. "He changed a lot and I was part of that, and proudly so."

The movie gets much of its verve from the major parallels between the careers of Keaton and his character. Thomson worries that he is stuck in the 90s — "I'm an answer to a Trivial Pursuit question," he laments — and has had to watch younger actors such as Robert Downey Jr. and Michael Fassbender take his place.

Inarritu, whose earlier films include "Babel" and "21 Grams," said he cast Keaton in part because he was one of the "few people in the world (who) has authority to talk about that" experience.

"Birdman" is one of 20 films competing for the Golden Lion top prize at the festival, which runs to Sept. 6. Whether or not it wins, many critics predicted it would be a hit — and re-energize Keaton's career. Variety labeled Keaton's performance "the comeback of the century," while Britain's Daily Telegraph called the movie "grand, spectacular, star-powered cinema."

It is a genuinely unusual film that mixes backstage comedy, philosophical musing and explosive special effects.

Keaton's character is torn between his desire to make high art — with a stage play based on a story by Raymond Carver — and an instinct to tell art to take a hike and focus on fame. His baser instincts are voiced by his Birdman alter-ego, who seems to live inside his head, and at times follows him around.

"I wanted the humor to come from his solemn ambitions to succeed, despite this reality that is proving to him that he will never do it," Inarritu said. "Which is basically the story of every human being, every one of us, every day."

Keaton said his character is "wonderfully pathetic and at the same time noble," and his foibles are matched by those of the other characters.

Edward Norton plays an actor who is talented and obnoxious in equal measure, Emma Stone is Thomson's disillusioned daughter and Amy Ryan his ex-wife. Naomi Watts, Andrea Riseborough and Zach Galifianakis play members of the troupe trying to put on the play.

"Birdman'''s cinematographer is Emmanuel Lubezki, who won an Academy Award for "Gravity," but it's style is light years from that high-tech space thriller.

Shot in long takes full of movement and zingy dialogue, the film sometimes feels like it could be by Robert Altman or even Woody Allen, though Inarritu's surrealist sensibility adds spice.

Keaton said he was frequently "petrified." Stone — no stranger to superheroes from "The Amazing Spider-Man" films — fared even worse: "I developed an eye twitch."

"I was terrified," she said. "And when it ended all I wanted to do was go back and do it again."

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