"Larry David: Curb Your Enthusiasm" could be the most unusual comedy special of the year. Not the best--oh no, not by a long shot, not in a pig's eye, not remotely--but still the most unusual. And considering the punishing sameness that afflicts television, "most unusual" is a plus.

Besides, Larry David deserves a certain amount of leeway. America owes him a great debt, not that he hasn't already collected millions and millions of dollars for what he did. He co-created "Seinfeld," one of the greatest and most idiosyncratic sitcoms of all time. He supervised the writing, is largely responsible for the loony mood of the show and was the inspiration for the character of George Costanza as played by Jason Alexander.

"Curb Your Enthusiasm," premiering on HBO Sunday night at 10 (with repeats scheduled for Oct. 25 and 28 and Nov. 3), is supposedly a combination documentary and comedy concert starring David, who was a struggling stand-up comic until about 10 years ago. Despite all his success, he's still struggling.

Jerry Seinfeld himself is among those appearing in brief interview clips talking about David. Fame and money haven't changed him, Seinfeld says: "This guy proves you are what you are."

Alexander recalls playing a scene as George Costanza during the filming of a "Seinfeld" episode. He wasn't comfortable with the dialogue or the way his character was reacting, Alexander recalls, because he felt no one would ever react that way in real life. Then David informed him that the incident was based on something from his own life and that he had reacted precisely that way.

The show is a mess but in a kind of amiable way. We see David and his manager selling their idea for a special to HBO executives (all--or most--played by actors); he'll do a comedy concert in a big theater, taped for telecast on HBO. Everything goes very well for about five seconds. Then complications set in because, as most alert earthlings know, complications always set in.

When David's one-hour program is 52 minutes old and there's still been no sign of the concert, it's obvious he is going to back out at the last minute. To do so, he tells a big fat lie that isn't even original. It's a lie he basically borrowed from someone he met at an airport earlier. We do get a few glimpses of David standing onstage telling jokes, warming up for his concert at comedy clubs like Caroline's in New York. His humor, as comic (and former "Seinfeld" writer) Carol Leifer notes, is hardly "mainstream." One of David's jokes begins: "The one thing about Hitler that I admire is . . ."

Another routine he does is based on the following premise: "It's a good thing they didn't have answering machines" in the Old West "when they were trying to form posses." When David shouts a punch line, he sounds a lot like Seinfeld; clearly they are blood brothers of comedy.

Interspersed with the comedy-club excerpts are scenes of David preparing for his concert, a film crew trailing him around. They capture such moments as David's manager pitching a fit at a hotel checkout desk because, although HBO has agreed to foot the bill, the company doesn't want to pay for porno movies that David watched on pay-TV in his room. Very funny.

Thanks to television, we already know much more about show business than we need to know. David's special suffers from the "inside baseball" curse. But it does offer a peek into the life and mind of a brilliant creative talent who is also clearly a huge pain in the neck and has no TV presence whatsoever.

Inarguably, the cranky and misanthropic David has the comedy gene. It's part of his DNA. It may also be what kept him from becoming a menace to society instead of a writer.