"A known actor comes with baggage, and Superman as a character is much larger than any actor," said "Superman Returns" director Bryan Singer, who settled on Routh, an actor with just a soap-opera stint and a handful of television guest spots. "He looked like he stepped out of a comic book. Brandon's an extremely fine actor, but he also needed to have the physical presence of someone who steps out of the collective perception of who Superman is."
Borrowing from the look and style of the Christopher Reeve "Superman" franchise that took flight in 1978, "Superman Returns" also follows that movie's pattern in casting. Reeve was an unknown who took third billing to Brando as Superman's Kryptonian dad and Gene Hackman as villain Lex Luthor.
"Superman Returns" gets its star power from Kevin Spacey as Lex. Spacey won the first of his two Academy Awards for his previous collaboration with director Singer, "The Usual Suspects."
Oscar winners such as Brando, Hackman and Spacey can add to the luster of a campy comic-book adaptation. But it's better if the guy in the cape and tights comes free of celebrity history.
"I think there's definitely something to that. Superman is such an icon that it's weird to even imagine myself as him," Routh said. "I think it helps that when people look at me in the film, they maybe see a little Brandon Routh, but they mostly just see Superman for right now. It's very important for the character."
"It's nice to introduce somebody unknown to an audience, so they can make the role their own, and it's not, 'Oh, he's the boy from this or that who played so and so,"' said Geoffrey Sax, director of the upcoming family action flick "Stormbreaker," based on the best-selling series about a British teen who becomes a superspy.
The lead role went to newcomer Alex Pettyfer in one of Britain's most-anticipated casting announcements since Daniel Radcliffe was picked to play Harry Potter.
A character sometimes can overwhelm an actor, even long after a film franchise has been laid to rest. Reeve took on a variety of roles to avoid typecasting, but his career always was defined by Superman.
Ford managed to break out of Han Solo's shadow after "Star Wars," but even that franchise's creator, George Lucas, initially was reluctant to cast him as Indiana Jones in "Raiders of the Lost Ark."
"Star Wars" co-stars Mark Hamill and Carrie Fisher never quite separated themselves from the Luke Skywalker and Princess Leia mantles.
It remains to be seen what sort of career Hayden Christensen, who shot to instant celebrity when Lucas cast him as the young Anakin Skywalker/Darth Vader, might carve out after "Star Wars."
Christensen has taken a broad range of roles, but he may have trouble distancing himself from the Vader persona, unlike co-star Natalie Portman, who had a body of work behind her before "Star Wars."
"I didn't go from like zero to 60 in like seconds or whatever," said Portman, who made a critical splash with her film debut in "Leon, the Professional" at age 13 and gradually grew into a mainstream star. "He's a wonderful example of someone who really dealt with it well. He's a really, really good person with good values and doesn't buy into the bull of it all, so he handled it really well. It's scary. It's a weird thing to go through."
Still, few actors would turn down an iconic role in a big Hollywood film for fear of the pressures of instant stardom.
Back in 2000, Hugh Jackman showed up for work on the romance "Someone Like You" and wondered who the 15 paparazzi milling about were waiting for.
"I walked about a block and realized all the cameras were trained on me, and I realized, `Oh, it's me,"' said Jackman, who had just shot to stardom as Wolverine in "X-Men" and now reprises the role in "X-Men: The Last Stand."
"Prior to that I'd done theater and films in Australia, which hadn't seen the light of day outside Australia. This movie was my first break, and it's very fair to say it was a monumental break. That movie changed everything for me."
Before the modern age of the franchise film, fresh faces emerged the old-fashioned way, with a bravura performance that had audiences asking, "Who is that?"
Audrey Hepburn had small movie roles before starring opposite Gregory Peck in "Roman Holiday," which earned her the best-actress Oscar. Brando was a stage star in the 1940s who became an overnight film sensation on the strength of his screen debut in "The Men," quickly followed by "A Streetcar Named Desire." Julie Andrews also had been a stage star when she made her Oscar-winning film debut with "Mary Poppins."
Stage performers still occasionally leap to movie stardom — if the right person from Hollywood is in the audience.
M. Night Shyamalan had been looking for the perfect young woman to play the spirited blind heroine of his creepy fable "The Village." Attending the theater one night in New York, Shyamalan found her — Bryce Dallas Howard, daughter of filmmaker Ron Howard, himself once the fresh-faced child star of "The Music Man" and "The Andy Griffith Show."
"For me, it was the moment I saw her on stage. I was just, `That's the girl,"' said Shyamalan, who also cast Howard in his upcoming summer film "Lady in the Water." "I actually believe she's a leading lady, which is a rare thing in this day and age. She's an old-school star, like the '20s, back when the big stars were women. Lillian Gish. She's that."
Nowadays, many of the big stars are superheroes, and as with "Superman Returns" or the "X-Men" movies, their casting is followed obsessively by fans.
The last thing a studio wants is millions of devotees grousing over the Internet that the filmmakers picked the wrong guy. An unknown makes the job easier, coming to the part with a stranger's mystique and little or no prior celebrity by which to be judged.
"The bottom line in those kinds of movies is that Superman is the star of the movie. It's not so-and-so as Superman," said producer Jerry Weintraub, whose 1982 film "Diner" helped introduce such fresh faces as Mickey Rourke, Ellen Barkin and Paul Reiser. "I'm doing `Tarzan' next year, and Tarzan is going to be an unknown, because Tarzan is the star, not the actor."
By David Germain