Gary Levin

USA TODAY

Even by showbiz standards, the deal moved with lightning speed: Six days after David Letterman told CBS he plans to pack it up next year, the network's CEO, Leslie Moonves, had a replacement lined up, following a frantic round of calls at the Final Four. Comedy Central star Stephen Colbert will be the new (and only second) host of Late Show, stepping into the role sometime next year.

But the mock-blowhard conservative character that earned his fame for the past eight years on The Colbert Report — and before that on companion The Daily Show — will fade away when he leaves the job in December.

"What you're going to get is the real Stephen Colbert," Moonves says. "He said it's time to do something different. If he's going to be on our air for 20 years, as we all hope, it's not humanly possible to keep that character going."

Colbert is the latest (and possibly last, for a while) chess move in a generational late-night TV shake-up that's seen stalwart Jay Leno retire, twice, and had two Jimmys — NBC's Fallon and ABC's Kimmel — move an hour earlier to compete against Letterman, with Fallon expanding Leno's longtime lead. Meanwhile, cable shows like Colbert's have eaten away at the audience, particularly among younger viewers. Colbert's typical viewer is 42; Letterman's, 58.

Still being worked out is the precise format of the new show, its staff and its location, though it will most likely remain in New York. "He's got ideas in his head, but we haven't gotten into, basically, a lot of what this show would look like," Moonves says. But he calls Colbert the "logical" successor to Letterman, still considered the dean of late night even with diminished ratings. "I think he'll be a phenomenal fit. He's intelligent, thoughtful, funny, and he'll be the guy who does social commentary. This is going to feel very different from the Jimmys."

On Thursday night's edition of The Daily Show, host and Colbert pal Jon Stewart said, "I think Stephen Colbert is up for the challenge." He added, "While we wish Dave (Letterman) the absolute best for a well-earned retirement, there's no greater joy for seeing a genuinely good man who works as hard as he can every day and deserves all the success in the world actually get that success. For Stephen, we're just thrilled."

Robert Morton, a late-night veteran and Letterman's former producer, says Colbert is "the only person I could conjure who would be a suitable replacement. I love that they're putting someone smart and curious, not fluffy and not the flavor of the day, but someone really substantial in there. It gives me hope for mankind and for network TV."

Letterman himself blessed the pick, who was Moonves' only choice for the job: "Stephen has always been a real friend to me," he said in a statement. "I'm very excited for him, and I'm flattered that CBS chose him. I also happen to know they wanted another guy with glasses."

On his own show Thursday night, Colbert dished out praise for Letterman as having "influenced every host who came after him, and even a few who came before him." He added, "I gotta tell you, I do not envy whoever they try to put in that chair."