On "Listen Up," Jason Alexander (search) plays a sitcom version of real-life TV sports talk host and newspaper columnist Tony Kornheiser. His character, Tony Kleinman, is a sports fanatic.

Before taking the role, was he familiar with Kornheiser?

"No, not at all," the actor admits. "I really follow sports very minimally."

Maybe that's why they call it acting.

Of course, Alexander got famous acting the part of hothead single guy George Costanza on "Seinfeld (search)." But on "Listen Up" (airing Monday at 8:30 p.m. EST on CBS), he's a family man with a knowing wife (Wendy Makkena) and two precocious teenage kids (Daniella Monet and Will Rothhaar). Malcolm-Jamal Warner (search) plays the sidekick on his talk show, "Shut Up and Listen."

Remove the laugh track, and Tony Kleinman seems all too similar to Tony Kornheiser, a Washington Post and ESPN fixture whom Alexander dutifully researched before filming began.

"I read his columns, watched his show. A funny man! I didn't know what he was talking about, but I enjoyed the hell out of him."

"Listen Up" is Alexander's second try at a sitcom comeback. Three years after the groundbreaking "Seinfeld" ended, he landed on ABC in 2001 playing a self-help guru on the eponymous "Bob Patterson." It quickly flopped.

"I was always interested in trying again, because I do like doing a sitcom," says Alexander.

Doing his new sitcom, he is borrowing from his past as George. But it's an early phase of the evolution process, "in the same way that I was doing a blatant Woody Allen impression when I started playing George — until I really understood that he was (`Seinfeld' co-creator) Larry David's alter ego, and the character could take on his own life. Tony Kleinman is in the nascent stage of becoming someone who isn't George."

Astute "Listen Up" viewers can already detect a softening of Tony's behavior from his cartoonish excess in the pilot episode.

"I look forward to growth in this character, of finding something uniquely different from where I started," Alexander says. "If you have the luxury of time, something really fresh and interesting can develop."

He notes that Kleinman is closer than Costanza to who he really is.

"I was never George," says Alexander. "I never had friendships like his. I never dated; I met (wife) Daena when I was 19." He has two sons. "Now I can go to work and offer suggestions to a writer: `A teenage boy wouldn't do that.' This is a world that I understand a little better, and that's kind of neat."

Not that anyone would confuse the actor with any of the sitcom characters he's played.

"The truth is: The real me is pretty shy, sober and serious about stuff," Alexander says in his typically quiet manner. "I don't have the sort of ego that makes me prone to those kind of outbursts. To do that, you have to feel, at least in the moment, INCREDIBLY right" — he is revving into moderate George-mode — "and to look at the world and go, `YOU are wrong, and not only are you WRONG, you're INSANE, and the madness has to END. And I'm here to END it!'

"I usually see the gray of everything," he sighs, "so it's hard for me in real life to make that kind of bold stand. But it's fun to play those guys!"

It was certainly fun to play George during the phenomenal 1990-98 run of "Seinfeld."

Although an uncertain starter, "Seinfeld" hit its stride with "The Contest" (which in November 1992 unveiled a new meaning for "master of his domain"), says Alexander. "But, not to be coy about it, we never truly either felt or expressed among each other any acknowledgment of the full impact the show was having."

Alexander doesn't count on starring in another series that will rise to "Seinfeld's" stratospheric heights. That's fine. At age 45, he says he embodies a more mature approach to success.

"True happiness occupies a very even, middle keel," he declares. "That's my experience of this show: even, constant joy and rewards. It will never burn as bright as the one that came before it, and there was a time when I would have said, `Oh, that's disappointing to me.' Now I go, `That's real to me, and just fine.'

"But it will be arguably less fine to people who haven't made that journey with me," he hastens to add, and its lukewarm ratings thus far ("Listen Up" is ranked 31st in viewers) may bear him out. "For the people who hold on to `Seinfeld' and George, they may want to live those highs that `Seinfeld' gave them every week — and the subtle joys of this show will probably elude them.

"So I must actually find a completely different audience for this show," he muses. "Who knows if I can do that?"