A sense of humor is a terrible thing to waste. Judd Apatow has become a Hollywood powerhouse, having written and produced successful comedies for TV as well as the big screen and, in the process, establishing a stable of performers and writers. His two directorial efforts, The 40 Year-Old Virgin and Knocked Up, were particular hits with critics and moviegoers.

Only a filmmaker in a position to write his own ticket would make a movie as protracted and self-regarding as Funny People. More of a dramedy or dark comedy than an outright yuk-fest, it revolves around a popular comedian named George Simmons, played by Adam Sandler, who is diagnosed with leukemia. A major celebrity yet fundamentally alone in the world, George proceeds to befriend Ira Wright, a struggling stand-up comedian limned by Apatow regular Seth Rogen.

For most intents and purposes, Sandler is playing himself -- a middle-aged film star who has achieved fame and fortune, mainly in silly vehicles where he portrays an infant or a creature that's half-human, half-mermaid. He doesn't like to be alone -- hence the groupies he's continually bedding (unlike the happily married Sandler, one presumes) -- and growing up could never make his father laugh. Ira is definitely not a stretch for Rogen. He works in a supermarket deli by day and at night hones his routine in LA clubs like the one in which he encounters George, who does a morosely self-pitying set soon after learning about his dire medical condition.

Unable to afford his own place, Ira sleeps on the pullout couch in the apartment of two pals. Mark (Jason Schwartzman) plays the lead on an inane sitcom called "Hey Teach" and Leo (Jonah Hill) is a fellow stand-up comedian, marginally more successful than Ira. George hires Ira to be his personal assistant and to write jokes for him, which also entails performing his own stuff before bigger audiences. They bond as Ira helps George endure the experimental drug therapy prescribed by his doctors. During the last hour of the picture, Ira is by George's side as he attempts to insinuate himself into the life of his former fiancée Laura, played by Apatow's real-life spouse Leslie Mann.

Credit the writer-director-producer for tackling more mature subject matter than in his previous outings: the spiritual angst of a middle-aged man feeling his mortality and lamenting personal mistakes. That suggests it won't speak to younger moviegoers and Apatow in effect tries to hedge his bets by riddling the film with his usual scatological and sexual humor, material befitting a sixteen-year-old boy or a forty-something man who still has doubts about his sexuality. 

Whether or not that humor is to your taste (in other words, whether or not Sandler and Rogen's past work is up your alley), the wit on display here can't survive the dreadful excursion north to the Bay Area as George pursues the woman he let get away. Laura is stuck in an unhappy marriage, to a roving businessman played by Eric Bana, and has a beautiful home and two daughters (played by Apatow and Mann's own offspring).

Allowing for the difficulty of successfully mixing comedy and drama, Apatow's Achilles' heel once again is structure. Formally, Funny People is a mess. Not only are the tech credits serviceable and the pacing awkward, there's no sense of proportion. The stand-up sets are strangely truncated, presumably to save the best jokes for the body of the film, and the awkward final hour is painfully elongated. Yes, on occasion you'll feel the sad clown's joy and pain, but after sitting for such a long time won't be able to feel your own rear end.

Sandler's performance is above reproach. He delivers some entertainingly silly jags and, as he showed in Paul Thomas Anderson's Punch-Drunk Love, is capable of understatedly piercing serious moments. What's grating about the film is its self-reflexiveness and insiderish feel. Apatow casts his usual jaundiced eye on the entertainment business without hiding his love for it -- even for the bad sitcoms like "Hey Teach." Enough with all the snide references to the dross and appearances by C-listers (Andy Dick being at the top of the list)! Combined with the semi-autobiographical storyline, it feels too incestuous.

As the saying goes, "You write what you know." In which case, get to know something else. Funny People is the ultimate sad-clown movie. Problem is, you're unlikely to emerge having felt the solace of showbiz, since Apatow's clown hasn't made you laugh or cry in the right measure.

(Released by Universal Studios and rated "R" for language and crude sexual humor throughout, and some sexuality.)