The May 17 hourlong season finale of Will & Grace sums up the tensile strengths and hairline crack weaknesses in one of TV's few rock solid sitcoms. It's an episode built around subplots old (Sean Hayes' Jack tries to find the father he's never met), subplots new (guest star Woody Harrelson, who first appeared on April 26 as a neighbor in Will and Grace's apartment building, steps up his wooing of Debra Messing's Grace), subplots borrowed (familiar sitcom shtick about Harrelson's Nathan asking Grace to ''rate'' him as a lover), and subplots blue (there's a reference to Jack's package as ''James and the giant peaches'').
But this expanded ''W&G'' fares much better than most sitcoms stretched to a ''special'' hour, due to the script by the show's creators, David Kohan and Max Mutchnick, and direction by James Burrows, perhaps the best director the genre has yielded. (Name another who's orchestrated verbal humor and slapstick more artfully than he who oversaw many of the best episodes of ''Taxi,'' ''Cheers,'' ''Frasier,'' and now every ''W&G.'') Instead of playing out like a stretched Silly Putty of a normal edition of ''Will & Grace,'' the finale maintains a ceaseless flow of sight gags and punchlines.
When, for example, Harrelson's loutish, aggressively straight Southerner Nathan gets loaded with Will and Jack, and Grace finds them sprawled on a bed together the next morning, she fears for her new boyfriend's sexuality. ''Grace,'' says Nathan breezily, ''if you're gonna think I'm gay every time I pass out with men, you're in for a world of heartache.'' Kohan and Mutchnick have long proven themselves masters of bitchy repartee, but with characters such as Nathan, they (to paraphrase T.S. Eliot) do the rubes in different voices.
The paradox of ''W&G'' -- its marvel and its trap -- is that it revolves endlessly around the same four people (Eric McCormack's Will, Messing's Grace, Hayes' Jack, and Megan Mullally's swizzle stick sarcastic Karen) in essentially the same locale: Will and Grace's apartment, with occasional visits to Grace's interior design office. Except for Karen's feisty maid, Rosario (Shelley Morrison), the series hasn't really introduced strong supporting players in the way that, say, ''Seinfeld'' had a supply of recurring oddballs like Newman the postal worker. On ''W&G,'' Gregory Hines, who started out with great promise as Will's boss last season, has vanished; his love interest subplot with Grace never jelled.
Indeed, the fact that no romances have ever jelled has left the show open to criticism it may not deserve -- after all, why must light as a soufflé ''W&G'' bear the weight of presenting successful gay liaisons just because half of its characters are homosexual? On the other hand, Will's crushed crushes (foremost among them, a short story arc with Patrick Dempsey) and Jack's one night stands with tight pantsed trash are getting a bit tiresome -- but then, so is straight Grace's inability to land a steady feller. You know it's not gonna be Nathan -- Harrelson has a movie career to tend to -- so the finale's cliff hanger is something of a letdown.
But the ''bad luck in love'' subtext has inspired some of the season's best episodes, such as the one in which the characters' bickering led Will to snap a truth at Grace: ''You're so content to play Mrs. Will Truman!'' The thing is, Kohan and Mutchnick have created a vivid quartet whose comic potential is actually lessened whenever anyone else barges into the apartment. How long, though, can the show maintain its witty pulse? I'm a little dismayed, for instance, that Karen calling Will ''Wilma'' for the umpteenth time still elicits a big laugh from the studio audience. I worry that such a consistent response, combined with the show's instinct for jokes that define male characters by female, ''sissy'' traits, plays into the stereotypes the creators want to subvert.
And yet one scene of Will and Jack at a gay disco on the April 26 show was more fun and sociologically acute (with its quips about music, pickup lines, and boogie down etiquette) than a whole season of Showtime's ''Queer as Folk,'' so should I complain? When even the throwaway jokes are hilarious -- such as when, apropos of absolutely nothing, Karen says to Jack, ''Honey, are you wearing base?'' and Jack murmurs back, ''A li'l bit'' -- you've just got to surrender to the pleasure.