The character of Superman is one of the most iconic, quintessentially American creations of the 20th century, so it's hardly surprising that the Man of Steel has enjoyed an enduring public life. Since he first appeared on the pages of DC Comics in 1938, Superman has evolved from a wisecracking tough guy into a genial movie hero whose overwhelming goodness compensates for his somewhat-questionable fashion sense (it takes a real man to wear a blue-and-red body stocking and cape). He has made stars of the actors who have portrayed him, from George Reeves to Christopher Reeve, and earned plenty of cash for the movie studios and TV networks responsible for his big- and small-screen iterations.

Intrigued by Superman's legacy, "Smallville" executive producers Mike Tollin and Brian Robbins partnered with showrunners Alfred Gough and Miles Millar to hatch a series that would reintroduce the character to a new audience. Their concept placed mild-mannered Clark Kent in rural Kansas, where he would face off against the perils of a "super-adolescence" -- including dating, exams and X-ray vision.

The show proved a perfect fit for WB's predominantly teen demographic, and four-plus seasons after its 2001 debut and with its 100th episode set to air tonight, "Smallville" has become a stalwart of that network's lineup, delivering solid ratings despite time-slot shifts and executive turnover. The show now airs Thursdays at 8 p.m. and routinely draws more men 18-34 viewers than does CBS' reality hit "Survivor" -- and, in perhaps the surest sign of its strength, "Smallville" was cited immediately this week as one of the strongest assets available to the CW network to be created in the fall by the union of WB and UPN.

The series' Seasons 1-4 DVDs also have brought in more than $100 million in revenue for Warner Home Video, according to Home Media Research, and "Smallville" has fared nicely in syndication for ABC Family, which picked up the show for about $400,000 an episode and began airing it in 2004.

Oddly, the creators of the sci-fi drama did not initially set out to make a show about Superman. Robbins notes that he and Tollin had their eye on a much darker, though equally compelling, comic-book character.

"In the early days of our deal at Warner Bros. (Television), we had the idea to do a young Batman," says Robbins, whose production company with Tollin, Tollin/Robbins, is also behind the WB drama "One Tree Hill."

Fortunately for Clark Kent, Warner Bros. Pictures already had spoken for Bruce Wayne's caped crusader: The studio then was developing "Batman: Year One," based on Frank Miller's graphic novel, for Darren Aronofsky to direct (though Christopher Nolan's "Batman Begins" ultimately would restart that film franchise last summer). It was suggested that Tollin and Robbins instead focus their series on Superman, a notion motivated in part by corporate synergy because the studio, the network and DC Comics are all owned by Time Warner.

"We wanted to do the same spin: Redefine the early mythology of Clark Kent," Robbins says. "We went to (WBTV president) Peter Roth, and he loved the idea -- and that was the beginning of it."

Finding the right actor to portray Clark Kent was critical, and even up-and-coming thespian Tom Welling understood that the role was not one to take lightly.

"When Tom Welling walked into the casting office, all we had was a tape where he played the cute pizza boy in (the 1997 movie) 'Chasing Amy,' I think it was," Tollin says. "He had a sparkle and charm and a screen presence, but he was a little concerned with diving in and playing a young Superman because, let's face it, this town is littered with people who have taken that on and found it was a dead end. To his credit, he wasn't a young actor who got stars in his eyes and said, 'This is my shot' -- we had to talk him into the role."

Obviously, Welling signed on, as did Kristin Kreuk as love interest Lana Lang and Michael Rosenbaum as a young incarnation of Superman's nemesis, Lex Luthor.

"Before this, I was doing comedy," Rosenbaum says. "Now, I'm the most serious character in the show -- but I do have fun. When we started, they said, 'We know you're eventually going to be evil, but let's make it interesting (and) see how the villain becomes the villain."

Once its elements were in place, "Smallville" became the subject of a major bidding war between WB and Fox, which did nearly everything it could to wrest the series from its rival. The struggle forced WB to make the show's creative executives an attractive offer: a 13-episode commitment with a significant budget.

"It worked out for the best because it really became a defining show for (WB), a defining show for us, and the slant we took on the show -- very youth-driven -- worked really well for them," Robbins says.

"Smallville" had the mixed blessing of debuting shortly after WB had lost "Buffy the Vampire Slayer," one of the gems of its schedule, to UPN and was in need of a smart, genre-bending, youth-skewing series with potential to garner critical acclaim. Although considerably different from "Buffy," "Smallville" similarly relies on the supernatural as a metaphor for growing up and assuming the responsibilities that accompany adulthood.

The premiere was anything but small in ratings terms: In a 9 p.m. Tuesday berth, "Smallville" delivered the best numbers for a series debut in the then-seven-year history of WB, bringing in 8.4 million total viewers, topping Fox and ABC in the time slot and delivering WB's best-ever numbers among adults 18-34 (4.5 rating/12 share), men 18-34 (5.0/14) and men 18-49 (3.9/10). It also ranked No. 1 in the time slot in WB's target demos of teens, female teens and persons 12-34.

After a rocky first season marred by on-set anxiety, "Smallville" assumed the mantle of a hit series with relative ease. The show seldom has been WB's flashiest asset but has proved its worth in every slot in which it has been scheduled, a trend that was underscored when "Smallville" moved to Wednesday nights in 2003.

The series' latest schedule shift, which took effect for the 2005-06 season, not only raised eyebrows within the industry -- could "Smallville" compete in the Thursday 8 p.m. slot against "Survivor," Fox's teens-in-peril franchise "The O.C." and other established hits? -- but also motivated its creatives.

"Believe me, last May or June, when we knew we were changing nights again, it was a nerve-racking time," says executive producer Greg Beeman, who has directed more than a dozen episodes. "I also think that because we were moving nights, we made a really concerted effort to have a great season. Obviously, that's the goal every season, but this year it was like, 'This is do-or-die for us.' What we all started talking about was how we were going to stop holding back on all the things we've been holding back on."

According to insiders, at least one character will die during tonight's episode, and Clark will not only propose to Lana but also reveal his true identity. "All those things that we've been playing with and flirting with, I think we all decided to just go for broke," Beeman says.

Perhaps that full-blown commitment to resolving story lines has helped to keep audiences hooked to "Smallville." The show's fifth season has been a boon to WB with an average total viewership of 5.5 million, up 28% from the 2004-05 tally, according to Nielsen Media Research.

David Bianculli, a TV critic for the New York Daily News and the National Public Radio program "Fresh Air," asserts that "Smallville's" unique brand of drama puts it squarely on his must-TiVo list.

"There are episodes and performances and ideas that I just like in this show," he says. "The idea of building a parallel new mythology for a familiar comic-book story is a nice use of entertainment television."

Adds Robbins: "Superman is a huge pop franchise, but Al and Miles have done a great job in writing and crafting it -- it's very well-executed. All of the new mythology that they brought to it -- the peeling away of everything slowly, playing out the Lex-Clark relationship slowly -- has really done the show a service."