Bob Costas will become the regular substitute host on CNN's "Larry King Live," the cable news network announced yesterday.

Expect to see Costas filling in about 20 times a year on the prime-time show; his first appearance is scheduled for Sunday.

Both Costas and CNN/U.S. President Jonathan Klein denied that this makes Costas the heir apparent to King on CNN's most watched program. King, 71, celebrated his 20th anniversary at the helm of the daily interview show last week.

"People will speculate about what they want, but that is not my intention," Costas, 53, told The TV Column, adding that he intends only to "do this and do it well and have a good time" and that he's "always liked the long-form interview format."

Costas hosted NBC's late-night talk show "Later With Bob Costas" for six years. (He also has been the prime-time host of NBC's Olympics coverage and covered many other sports events during his more than two decades at the broadcast network.)

The idea for the guest-hosting gig was HBO's, Klein told The TV Column. Costas hosts HBO Sports's monthly newsmagazine "Costas Now," and during football season he co-hosts "Inside the NFL" for the pay cable network, which, like CNN, is owned by Time Warner.

"The guys at HBO told us he had always been interested in this kind of thing and once we heard that we really pounced," Klein said.

That said, he insisted this was "not some effort at massive corporate synergy; it so happened that our friends at HBO work with Bob and knew of his interest."

Without HBO's blessing, Costas said, "this couldn't have happened."

Costas's guest-hosting appearances won't be on a set schedule, Klein explained. "Larry's vacation days . . . are very haphazard; he much prefers to work," Klein said, adding, "We'll always turn to Bob first as the main substitute host."

(Nancy Grace, the "Larry King Live" contributor who also used to sub for King, is now locked and loaded on CNN Headline News and has her afternoon show on Court TV.)

This calendar year, "Larry King Live" has averaged about 1.2 million viewers, but in May King's average dipped below 1 million, marking one of his least watched months of the past four years. (On the other hand, Fox News Channel's "O'Reilly Report" dipped below 2 million viewers last month for the first time in a year, so maybe May is not a great month for some cable news shows.)

"Bob's broad range of interests, his quick wit and his deft interview skills will engage viewers in the best King tradition," Klein said yesterday in a memo to his staff about the Costas hiring.

Another in our ongoing reports on Where in the World Is Dave Chappelle:

Dave Chappelle has been sighted meeting with a Comedy Central suit in Los Angeles.

It's the comic's first meeting with the network that's reportedly paying him upward of 50 million bucks for a third and fourth season of "Chappelle's Show" since he performed his Amazing Disappearing Act with exactly zero episodes completed. Turns out, Chappelle hopped on a plane to South Africa, forcing Comedy Central to scrub the highly promoted May 31 season debut.

Network spokesman Tony Fox confirmed an Associated Press report that that nice network president, Doug Herzog, met with Chappelle on Friday. He declined to reveal the exact location or what the two talked about, but we're guessing that $50 million and Seasons 3 and 4 were mentioned.

Two days earlier, Chappelle stunned customers of two Hollywood comedy clubs when he showed up unannounced, saying he'd just landed in L.A. and wanted to perform.

That's nearly two weeks after he'd raised eyebrows at Ye Old Trail Tavern in Yellow Springs, Ohio. Patrons told the Dayton Daily News that Chappelle had been spotted in town "just chilling and walking around with his friend."

That was about a week after a Chappelle sighting at uShaka Marine World ("The marine park is tastefully themed with African imagery and exudes an air of fun and excitement") on the beach of the South African port of Durban.

There, he told Time magazine's Johannesburg bureau chief that he had not checked himself into a mental health facility, as Entertainment Weekly had reported, but had dropped everything and traveled to South Africa to visit a friend, "take inventory" and whine to Time about how hard life is for him, what with making $50 million and finding that your "inner circle" has changed. Really sad stuff.

Not long after Chappelle was sighted at that theme park in South Africa, Herzog was quoted as saying that Comedy Central was no longer planning for a third season of "Chappelle's Show" in 2005. No word as of yesterday whether his chat with Chappelle last week did anything to change his mind.

And last week, while Chappelle was chatting with Herzog in Los Angeles, Comedy Central sold 400,000 more copies of the "Chappelle's Show" second-season DVD, for a total of 1.4 million copies to date. The first-season DVD has so far sold 2.9 million copies, making it the biggest-selling DVD of a TV series ever.

CNN expects that Bob Costas will fill in for Larry King about 20 times a year. His first appearance is set for Sunday.