CHICAGO — On a blustery fall afternoon, Andy St. Clair slips into an empty club, with rows of tables, wooden chairs and a bare stage awaiting its next bit of comedy magic.

It doesn't look like much, but the stage is something of a shrine.

This is The Second City, the place where legions of comics — among them Tina Fey, Stephen Colbert, Steve Carell, Mike Myers, Chris Farley, John Belushi, Bill Murray and John Candy — sometimes killed, sometimes flopped, but always tried to make 'em laugh.

This weekend, the theater marks its 50th anniversary, a milestone that's even more impressive in the ephemeral world of show business. Second City has survived and thrived for a half-century with the same formula: small, youngish casts; parody, satire and improvisation; and hip, irreverent, topical, often political humor.

Decades ago, it was Alan Arkin in a rain hat and slicker phoning God — "That's N-O-A-H," he tells the divine — and auditioning ark candidates. Thirty years later, it was Carell (Arkin's cast mate in "Little Miss Sunshine") as a job applicant ordered to disguise his voice so a blindfolded personnel manager can guard against biases.

Now it's Andy St. Clair's turn. He's at the Wells Street theater this day for rehearsals for the 97th main stage show, "The Taming of the Flu."

From one generation to the next, Second City has cranked out talent with clockwork regularity. "It's a comedy factory," says Harold Ramis, a former cast member turned director-writer-actor-producer.

The origins of Second City read almost like a TV pilot: A group of intellectuals, mostly from the University of Chicago, forms a comedy theater in a run-down former Chinese laundry at the end of the buttoned-down 1950s.

And then ...

Cue the laughter, right? In this case, yes, this was the start of a 50-year-plus run for a troupe that took its name from a snobby reference to Chicago in an A.J. Liebling piece in the New Yorker.

So what's the key to longevity for a theater that has mushroomed into a $30 million-a-year business with two locations (Chicago and Toronto), four touring companies, three training centers and alumni that have made a splash on "Saturday Night Live," "The Office," "30 Rock," movies and more — in front of and behind the cameras?

The explanation sounds deceptively simple.

"The reason it's successful is because we stay relevant," says Andrew Alexander, co-chairman and chief executive officer since 1985.

The revue titles bear that out. Among some recent ones: "Between Barack and a Hard Place" (the president and first lady both saw the show) and "No Country for Old White Men."

The Second City stage is a taboo-free zone, mining humor from Guantanamo and torture, 9/11 and terrorism, and less timely but equally grim subjects such as assassination and death.

Can a plot to bump off then-candidate Barack Obama be funny?

Yes, if it features a character called Sillary Tinton trying to hire an assassin. He declines, confessing he's smitten by Obama, who has a voice that "sounds like sandpaper covered in maple syrup and topped with chocolate chips."

And death? That's worth a laugh, too.

Consider a classic skit, "Funeral," written in the 1960s and still performed on tour. Mourners at a funeral slowly learn how the deceased met his untimely death: His head got stuck in a gallon can of beans.

"The best comedy touches something that's timeless and universal in people," Ramis says.

Pushing the envelope is part of Second City tradition. Just ask Sheldon Patinkin, who has been with the show all 50 years and is now artistic consultant.

He remembers one skit where robbery victims are waiting for Superman and when he arrives, he's in a wheelchair — shades of Christopher Reeve. "There was shocked silence, then enormous laughter," Patinkin says.

Second City humor isn't designed to shock, just to be funny. Skits deal with the fodder of everyday life — marriage, money troubles, neighbors.

"It's a direct reflection of the audience, commenting on the things that worry them, that concern them and finding some humor in them," says Bonnie Hunt, a former cast member turned talk show host, actress and director.

Hunt worked at Second City at night. During the day, she was a cancer nurse. She managed to blend both.

"I thought of Second City as just the greatest therapeutic job anybody could ever dream of having," says Hunt, who'd bring cast members and videos of shows to her patients.

In its earlier days, the troupe's University of Chicago roots meant a certain amount of intellectual humor — a mention, perhaps, of the philosopher Kierkegaard, along with jokes about football.

These days there are more sports and pop culture references, though there still is a heavy emphasis on Chicago, whether it's the hapless Cubs or the city's checkered reputation for politics.

One recent special show centered on former Illinois Gov. Rod Blagojevich, facing federal racketeering charges.

Second City exploded on the national scene in the 1970s with the popularity of "Saturday Night Live." The troupe's Chicago and Toronto casts became a comedy college for future SNL casts.

Early on, it was Gilda Radner, John Belushi, Dan Aykroyd and Bill Murray. Then Mary Gross, Tim Kazurinsky, Jim Belushi, Mike Myers, Chris Farley and Tim Meadows. Then Rachel Dratch and Tina Fey, among others.

As SNL was getting off the ground, another show, SCTV in Canada, was introducing comic talents such as Martin Short, Eugene Levy, Catherine O'Hara, Andrea Martin, Dave Thomas, Joe Flaherty and John Candy — all of whom were on Second City's Toronto stage.

One part of the show is improvisation, with topics suggested by audience members. They can be tough critics.

"I was booed off the stage — that was not fun," says George Wendt ("Cheers"), a cast member in the '70s, recalling a "poor taste" improvisation about nuns, priests and sex.

Wendt says improvisation didn't come easily. "I would find myself staring at suggestions and being a complete dullard," he says. He was demoted to the touring company, he says, by co-founder Bernie Sahlins. "He thought I was playing it too safe," Wendt says.

Wendt eventually returned to the main stage. "I finally gained some resolve from my first bit of adversity," he says. "It was helpful. I recommend getting fired."

Nia Vardalos ("My Big Fat Greek Wedding") remembers when she bombed.

After a skit, the lights went off, cast members retreated backstage momentarily and "it was like the worst feeling I ever had in my life. A minute later, I had to go back out there. It made you tough."

She got her Second City gig in an unusual way. She was working in the Toronto box office — she had auditioned three times — and when her duties were over, she'd watch the show. One day, she says, a cast member became ill, she got an on-the-spot audition of a skit, then amazingly went on. She was hired for another Canadian cast and later moved to the Chicago troupe.

Most cast members, though, come up through the training centers and a much smaller conservatory, then audition (sometimes several times). They usually start with a touring company or the smaller Chicago stage.

A rare exception was John Belushi, who zoomed straight to the main stage.

"He was just wonderful from the beginning," Patinkin says.

Not every Second City performer ends up in show business. Many have become homemakers, doctors, lawyers, even cops.

But there's always that ripple of expectation. Andy St. Clair knows it.

"Sometimes I'll sign a Playbill," he says, "and someone will say, 'I'm going to keep this signature. I look forward to seeing you on SNL (Saturday Night Live) next year.'"

So what's the future for Second City?

"I don't see any reason why it shouldn't go on," Patinkin says. "Satire is always relevant."

So mark 2059 on the calendar.

Maybe someone will be on the Wells Street stage, joking about a guy who died when his head got stuck in a can of beans.