While O'Brien is off to a perfectly solid start, he's had to overcome a bit of arthritic stiffness.

First, the obvious part: After 16-some-odd years of on-the-job training, Conan O’Brien knows how to host a latenight talkshow. The bone of contention has been that the one he’s begun overseeing at 11:30, also known as “The Tonight Show,” was initially less loose, fresh and consistently interesting than the version he hosted after midnight. That situation notably improved on Wednesday, which showcased much of the zip and irreverence characteristic of the old “Late Night.” So while O’Brien is off to a perfectly solid start, he’s had to overcome a bit of arthritic stiffness associated with that new chair.

Frankly, the NBC program figured to get better once all the hoopla, huge marquee guests (Will Ferrell/Pearl Jam, Tom Hanks/Green Day) and supply of advance “Welcome to L.A.” taped pieces subsided. Until night three, O’Brien exhibited only flashes of his “Late Night” self during his premiere week, much like a student who had too much time to cram for final exams.

Despite the extended standing ovations and audience cat calls (which are already growing a bit tiresome), the new “Tonight” had felt overly self-conscious and fastidiously planned. That drawback was mostly corrected in the third outing, which saw the host riff about NBC execs by petting an invisible cat — a la the Bond villain Blofeld; a walk-on appearance by basketball great Kareem Abdul-Jabbar; and the revival of O’Brien’s “In the Year 2000″ (upgraded to 3000) with sidekick Andy Richter. The best line: Twitter, Facebook and YouTube will merge into something called “YouTwitFace.”

O’Brien also looked more at ease behind the desk with the invariably adorable Julia Louis-Dreyfus, after Will Ferrell sort of hijacked the show on Monday and Tom Hanks dominated (in a more helpful way) Tuesday.

Although O’Brien isn’t as strong a monologist as predecessor Jay Leno, he has an ability to spontaneously create the show in a way that Leno couldn’t — and, indeed, showed little interest in doing. Yet while there’s doubtless been an attempt to woo the former “Tonight” audience with a broader approach as the show generates big sampling this week, the bottom line is that there’s no reinventing the wheel — or the talent.

Even if the ratings don’t reflect it, the week has also been a stellar one creatively for David Letterman, who looks reinvigorated by the shift at NBC. CBS’ cranky latenight lion in winter appears somewhat liberated, joking about losing out on “The Tonight Show” again and noting that North Korean dictator Kim Jong-Il has been offered “the 10 o’clock spot” to get rid of him. O’Brien came of age worshipping Letterman, and it’s not the worst thing to have two smart, funny guys going head to head.

Learning who emerges on top in the ratings will actually have to wait until the fall, when Leno premieres and the primetime landscape is realigned — creating a lead-in scenario that promises to favor Letterman, offering the host a chance to reclaim alpha-dog status. Because while O’Brien started off his “Tonight” tenure with a clever cross-country sprint, the latenight race, as everyone knows by now, is really a marathon.

The Tonight Show With Conan O'Brien

Series; NBC, Mon.-Wed. June 1-3, 11:35 p.m.

Production

Produced by Conaco Prods. in association with Universal Media Studios. Executive producer, Jeff Ross; producer, Tracy King; supervising producers, Frank Smiley, Daniel Ferguson, Rachel Witlieb.

Crew

Head writer, Mike Sweeney; senior talent executive, Paula Davis. 60 MIN.

Cast

Host: Conan O'Brien. Announcer: Andy Richter. Band leader: Max Weinberg.

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