THE BIG SWITCH NBC'S COURIC, LENO TRADE PLACES, TV SHOWS FOR A DAY.

Byline: DAVID KRONKE TV Critic

Just a suggestion to the producers of NBC's ``Today'': Next time you have a late-night comic co-anchor the program, try not to open it with the words ``Good morning - 'I've just killed my children.'''

Poor Jay Leno. This was opening of the first ``Trading Places'' edition of ``Today,'' in which the host of ``The Tonight Show'' switched roles with ``Today'' co-anchor Katie Couric, who hosted ``The Tonight Show'' later Monday.

``Today'' co-anchor Matt Lauer led the show with the 911 confession in the luridly tragic story of the Texas woman who had killed two of her children over the weekend. A story, mind you, that wasn't even leading the Web sites of major Texas newspapers.

Leno looked fairly grim. That would be a tough point to rally from, if being entertaining was the idea, and for Jay, that's always the idea. His first few exchanges were subdued affairs, and while he picked up steam - and the ``Today'' folks tried to encourage him by laughing at some pretty weak material (he referred to himself, Lauer and weatherman Al Roker as ``a bad Pep Boys'') - he didn't hit his stride until late in the broadcast.

By contrast, there was a party atmosphere in Burbank on the set of ``The Tonight Show,'' where Katie Couric - whose idea this whole ``Trading Places'' thing was in the first place - emerged onstage in a very un-anchor-like low-cut, sleeveless black dress and stiletto heels. Guests Mike Myers and Robbie Williams both greeted her salaciously - how could they help themselves?

And Couric loved it - pointing to her breasts, she announced, ``For all you people from L.A. who've never seen them before - these are actually real.''

``Great career move,'' ``NBC Nightly News'' anchor Tom Brokaw, rolling his eyes, advised Couric in a pre-taped segment. ``Let me know when you do 'Hollywood Squares.'''

It was Katie's coming-out party, complete with Chippendale dancers egging her on, and anyone who might complain that this further blurs the lines between TV news and entertainment certainly hasn't watched ``Today'' in a while.

Her timing wasn't as assured as a professional comics, but it was good enough, and Leno's writers gave her some decent material with which to work.

In contrast, the bit that ``Today'' came up with for Leno - prepping him on current events while he wore ``Today'' show pajamas - was downright embarrassing.

Let's face it: When you're America's Sweetheart, like Couric, it's not going to be too hard to look like a good sport, and Katie has ``Lovable With a Capital L'' down cold. She made jokes about both Leno's and Lauer's hairstyles (or, in the case of Lauer, lack of hairstyle), riffed with Myers about her cameo appearance in the most recent ``Austin Powers'' movie and, in a comedy bit with ``American Idol'' judge Simon Cowell, did a credible job playing a ditzy Paula Abdul, encouraging criminally off-key singers.

On the other hand, Leno fared poorly putting on something of a serious facade. While Lauer chatted up ``The Matrix Reloaded's'' Carrie-Anne Moss, Leno tackled Secretary of State Colin Powell in a pre-taped interview and former New York Mayor Rudy Giuliani live.

After somewhat awkwardly reminding Powell that he had interviewed him before on his own show - the subtext being: I do too belong here - Leno asked him, ``How is it to be diplomatic in the Middle East right now?'' That was a softball lob easier even than those he serves his bumptious celebrity guests on his regular show.

Leno's best moment was actually a noncomedic one. After watching some stunt drivers behind the wheels of two Mini-Coopers rather dully screech back and forth on a controlled lot, Leno assumed control of one and, with dieting weatherman Al Roker panic-stricken in the passenger's seat, burned some serious rubber in a series of spinouts and tight U-turns.

Afterward he joked, ``Al just lost 10 more pounds!''

Earlier, famed night-owl Leno said he hadn't slept at all that night - brilliant idea, having a sleep-deprived celebrity do automotive stunts!

Actually, Leno was at his best later, when he delivered a blistering monologue mocking NBC's top executives - revenge for making him participate in the gimmick, perhaps? - at the network's program unveiling of its 2003-04 schedule. It may have been the funniest he's been in years. But that performance was only seen by a few thousand industry insiders, not 6 million viewers.

Other ``Today'' stars will trade places with non-TV celebrities later this week. On Wednesday, newsreader Ann Curry will scrimmage with soccer star Mia Hamm's team the Washington Freedom while Hamm reports on the day's happenings.

Lauer will switch seats with a New York cab driver Thursday (presumably, he'll get a good night's sleep beforehand), and Roker will jump from TV's fire into a frying pan Friday, switching positions with a prestigious Big Apple chef.

CAPTION(S):

4 photos, box

Photo:

(1 -- color) As part of ``Trading Places'' on NBC's ``Today,'' co-anchor Katie Couric guest-hosts ``The Tonight Show'' during a taping in Burbank on Monday, here chatting with actor Mike Myers.

Paul Drinkwater/NBC-TV

(2 -- color) Jay Leno, left, host of ``The Tonight Show,'' joins co-anchor Matt Lauer live on NBC's ``Today'' in New York on Monday. Leno swapped roles for a day with Couric.

David Atlas/NBC News

(3 -- color) KATIE

(4 -- color) JAY

Box:

KATIE vs. JAY