If the era of vicarious reality is just around the corner, the age of vicarious entertainment is already at hand. The latest example is "Late Night With Conan O'Brien," an hour of aimless dawdle masquerading as a TV program and airing at 12:35 each weeknight on NBC.

O'Brien is the young unknown chosen by myopic NBC executives to inherit David Letterman's vacated time slot and Letterman's nicely outfitted studio (6-A) in Rockefeller Center. As unveiled on Monday night's premiere, the new couch-and-desk set designed for O'Brien looks like a cramped New York apartment, and O'Brien seems a switch on the guest who won't leave; he's the host who should never have come.

Subtract this fidgety marionette from the Lorne Michaels production and you have a fairly handsome talk show package waiting for a real entertainer to step in. O'Brien did show some signs of wit on his premiere -- mainly in prepared material -- but clearly he should be the head writer of the show, not the star.

O'Brien's sheepish underdog act had already worn thin before he got on the air, from promos and appearances on other shows, but virtually the whole first program was built around it; the show was about the show. First came a taped segment of O'Brien roaming New York and being told by everyone he met that he had to be "as good as Letterman" (no one is seriously expecting that) and that he was under a lot of "pressure."

He later goes to his dressing room and considers hanging himself, but instead decides to go on.

Participating in this protracted wheeze was anchor Tom Brokaw, who greeted O'Brien at an elevator and threatened him by crushing some soda crackers and blowing the crumbs into the air. Brokaw probably made this appearance to appease Robert C. Wright, the bumbling NBC president, who reportedly blew a gasket over the fact that Brokaw did a guest shot on Letterman's new CBS "Late Show."

But Brokaw should remember that a man can be too good a sport. The next step is to take a pie in the face.

As for O'Brien, the young man is a living collage of annoying nervous habits. He giggles and titters, jiggles about and fiddles with his cuffs. He has dark, beady little eyes like a rabbit. He's one of the whitest white men ever.

On opening night, O'Brien had the benefit of superior guests: John Goodman, who never fails to score on these shows; Drew Barrymore, looking fantastic; and, as a wry touch, talk show talisman Tony Randall, who only last week did a walk-by on Letterman.

Conan's one good impromptu moment was when he turned to Randall and asked, "You're not amused by me at all, are you?" But most of his remarks were trifling chatter or golly-gee guff like "wow" and "all right!" Goodman had already done one segment when, back from a commercial, O'Brien came up with this riveting query: "How's it goin'?"

He showed no real interest in anything anyone had to say, instead concentrating on the prepared comedy bits scattered through the evening. Some of these involved the guests, such as a "leg wrestling" match between Goodman and surprise guest George Wendt, or Randall joining O'Brien for a closing facetious chorus of "Edelweiss" from "The Sound of Music."

Likable Bob Costas also appeared, quite effectively, in a mock promo for his "Later" show in which he interviewed two surviving cast members from "The Wizard of Oz": an aged midget and a still-crabby apple tree.

The show itself was not a shambles, the way Chevy Chase's premiere was, but O'Brien is a kind of walking shambles all by himself. For the record, the Max Weinberg Seven, who provide the music, seem one of the best talk show bands going, but they could be the New York Philharmonic and not be able to save O'Brien from himself.

On the crowded set hangs a photo of the great Tom Snyder, whose "Tomorrow" show once occupied the time slot. On his own CNBC cable talk show Monday night, Snyder graciously congratulated O'Brien and plugged the show. One can look back longingly to the time when Snyder kept weary viewers awake with engaging talk from a wide variety of guests -- no band, no monologue and very little phony show biz shtick.

Snyder is a born broadcaster who can't seem to help but be fascinating on the air. Conan O'Brien is the precise opposite of that.