Big Dave Serves the Tastiest Fare on Late-Night : Television: Letterman’s McDonald’s drive-through bit is lofty nonsense that embodies his ease and success at CBS.

The network and time slot have changed. But David Letterman still delivers some of the loftiest nonsense on television, absurdity boosted to stratospheric art.

The other night Letterman hung out at McDonald’s. It was a bit, a wheezingly funny one in which he manned the drive-through counter, harassing and asking screwball questions of motorists who were trying to place their orders. He told one that McDonald’s had run out of onions, and would the guy please go out and get some more? Amazingly, he did, dutifully driving back through to deliver the sack.

Few customers appeared to recognize the Big Mac serving them, but when one did, Letterman told her that the deal with CBS hadn’t worked out, and well, you know, a guy had to make a living.

You see it in the host and you see it in his show. Like a pool shark running the table, “Late Show With David Letterman” now moves with ease, confidence and success.

Skeptics questioned whether Letterman could offer the same inventive goods at 11:35 p.m. on CBS--and still be competitive in the Nielsens--that he did at 12:35 a.m. on NBC. The issue is now moot, given his show’s performance level and its national ratings lead over “The Tonight Show With Jay Leno” (although Letterman trails both Leno and “Nightline” in Los Angeles).

Letterman still has his Top 10 list, of course. The No. 1 sign that you’ve hired a bad department store Santa, for example? “He’s packing heat.”

Although now tilted heavily toward the biggest stars, the guest list is still hit and miss, as is the grinning monologue. But the McDonald’s scam was classic Letterman, a symphonic echo of his former NBC show, in which his brilliantly conceived forays outside the studio often produced the biggest laughs.

Among his funniest moves these days are scripted “spur-of-the-moment” visits to neighborhood merchants. On Thursday, he ran outside to buy a $10 “Rolex” from a street vendor. It was a birthday gift for bandleader Paul Shaffer, a gifted farceur himself.

Later came another unique alumnus from the old show. A true visitor from Pluto, satirist Chris Elliott showed the first of the monthly films he’ll be doing for Letterman. With Elliott as a 1930s-style hitchhiking poet whose yammering drove a motorist (Paul Dooley) mad, it was sidesplitting.

Just as Ernie Kovacs and the early Steve Allen have influenced Letterman’s show, competition with “Late Show” has lifted the performance of “The Tonight Show.” Always a funny monologuist, and a better interviewer than he’s given credit for, Leno now pushes the talk show envelope in ways that Letterman has been doing for nearly a dozen years. Yet while supported at times by some devilishly good writing, Leno’s skills just don’t fit the goofy little routines that Letterman excels in.

Leno packs a mean opening monologue. From 11:35 to 12:35, Letterman packs heat.

Conan Update: When we last checked in on Conan O’Brien, Letterman’s late-night successor on NBC, he couldn’t deliver a monologue and couldn’t interview. He couldn’t do much of anything except be likable.

But on-the-job training is paying off. The update: Conan and “Late Night With Conan O’Brien” are getting better.

O’Brien still stumbles through his opening monologues, wasting good gags. He still can’t U-turn a bad interview into a good one. But he less frequently turns potentially good ones into bad ones, and sections of his show are now sometimes very funny.

On Thursday, for example, he had a grand time with feisty “Today” co-host Katie Couric. Plus, a couple of phony dog experts and O’Brien’s own “Laughing Genie”--in which he does nothing more than wear a costume and bellow laughter--were exactly the kinds of inventively written, charmingly bent silliness that can make O’Brien addictive.

And as a bonus, he’s still likable.

Rave Review: Flashback to the 5 p.m. edition of the KNBC-TV Channel 4 news on Nov. 27.

The critic knew something pretty terrific when he saw it.

The critic had fallen in love with “Hollywood’s Leading Ladies With David Sheehan.”

The critic showed clips and urged viewers to watch the NBC special when it aired on Dec. 4.

The critic praised the editing.

The critic praised the executive producer.

“We’ll have to get a sneak preview so we can talk about it,” said anchorman Kent Shocknek. No need. The critic was managing very well on his own.

The critic continued to praise the special and to show clips during Channel 4 newscasts on the subsequent Monday, Tuesday, Wednesday, Thursday and Friday. On Thursday night, he also praised the special in an appearance on “The Tonight Show With Jay Leno.”

During an earlier Channel 4 newscast that day, he gave an enthusiastic review to NBC’s “Rowan & Martin’s Laugh-In Past and Christmas Present.” Then he added: “NBC has a better special this Saturday. It’s called ‘Hollywood’s Leading Ladies.’ Please watch it.”

The critic seemed to be pleading.

“Nothing like shameless promotion,” said anchorman Jess Marlow.

“Nothing to be ashamed of ,” the critic responded. “I’m proud of it.”

Pride. Yes, that’s what the critic was all about.

The critic who reviewed “Hollywood’s Leading Ladies With David Sheehan” was, of course, Channel 4’s “entertainment editor,” David Sheehan himself.

Marlow was correct. What Sheehan did--give himself daily rave notices with a straight face--was shameless. It was shameless both for him and for the Channel 4 bosses who allowed him to do it. It was the kind of performance that could damage their credibility.

Oh, yes. What credibility?

Bawling for Dollars: Making the TV talk show rounds these days are glitter-eyed Tammy Faye Bakker and her new husband, Roe Messner. On “CBS This Morning” Friday, she told co-host Harry Smith that her imprisoned ex-husband, former TV evangelist Jim Bakker, was “sad” when she informed him she wanted a divorce.

Smith wondered about the timing of delivering such a devastating message to a man still behind bars. Tammy’s skewed spin: “I felt it was the kindest time to tell Jim that it has ended.”

Unending, though, is her goal of saving souls through another TV series, presumably like the evangelistic one she and Jim operated for years. She’s already doing it through her very own “900” line. “I really feel like I’ve got something to say to the people,” she told Smith. “I can really help people get out of bed and really make it.”

Amen. Thinking of Tammy while having a hard time getting out of bed Saturday, I dialed her “You Can Make It” line ($2.99 a minute) and was immediately uplifted by her inspirational recorded message.

“Hi, this is Tammy Faye,” she said before reviewing her life (“Such sadness. . . “). She said that her relationship with Jim crumbled after his imprisonment (for fraud), and she had to get out of the marriage “to save my mind.” So scratch Jim. “Him and I divorced,” she said.

Now she can concentrate on helping others. We should learn to face problems straight on, she lectured, and walk through life saying, “I can , I can , I can , I can .”

As always, Tammy is right. I can pay for this call.