(CNN) -- Comedy is hard; dying is easy. Any stand-up will tell you that.



Adam Sandler and Seth Rogen play comedians in "Funny People."



Let's have a hand, then, for Judd Apatow. Hollywood's most successful contemporary comedy producer isn't resting on his laurels but continues to push toward risky subject matter: male sexual insecurity in "The 40-Year-Old Virgin," unwanted pregnancy in "Knocked Up" -- and now the big C.



No, not cancer -- though Adam Sandler's superstar comedian George Simmons is stricken with an appropriately eccentric form of leukemia. No, this latest film's true subject is Celebrity and the funny things it does to people.



Apatow's most personal (and also most self-indulgent) film, "Funny People," shuffles between three competitive Angelino roommates scrambling to grasp a rung on the showbiz ladder (Seth Rogen, Jonah Hill, and Jason Schwartzman), Simmons' multimillion-dollar Malibu mansion and the L.A. comedy clubs that sometimes bridge the gap between anonymity and fame.



Apatow and Sandler know these worlds well enough. The movie begins, in fact, with old home video footage of young Adam goofing off, making prank phone calls while his roommate Judd sniggers behind the camera. It's one of the few times we see Sandler really having fun and cutting loose. This is mostly a restrained, subdued and admirably unsentimental performance.



It feels natural that Simmons -- faced with his dire prognosis -- should return to the comedy circuit to wrestle with his imminent extinction before a roomful of strangers, even as he decides to keep his condition a secret from everyone around him.



It's actually not so hard in his case because he doesn't have any real friends, only "showbiz friends."



The exception is Ira Wright (Rogen), a struggling young comic who lucks into a job as his hero's joke writer slash personal assistant. Simmons is by turns demanding, generous, friendly and abusive, and Ira couldn't be happier.



The cross-currents are intriguing: He's getting his first taste of the high life, just as George is trying to savor his last days by reliving his first steps on the circuit.



True to form, Apatow negotiates the perilous terrain of existential doubt with his fall-back weapon of choice, the penis joke. Some of these are choice (Ira's real last name is "Wiener," pronounced "Whiner"), but many, many more feel flabby and redundant.



There's even an Andy Dick joke, in the form of Andy Dick himself -- one of several celebrity cameos, the oddest of which is surely Eminem, wondering aloud if George wouldn't be better off dead.



We must be approaching the 80-minute mark by then, about the time many comedies start wrapping things up. But it's a question that doesn't seem to have occurred to Simmons or the filmmakers before, and it spurs Apatow on to develop another hour of additional material in which George, miraculously recovered, pursues the love of his life (Leslie Mann), Ira in tow, without much consideration for her two daughters or her husband (Eric Bana). It's as if the movie bred its own sequel.



There's plenty of funny stuff here. Bana has a ball as the obtuse Aussie, but despite all the blue jokes, this is a more modulated, pensive effort than Apatow's previous hits.



He's improved, a little, as a director (perhaps the credit belongs to cinematographer Janusz Kaminski, who ensures that for once it doesn't all look like a sitcom), but Apatow is still in dire need of a good editor.



His instincts are generous. He wants to give us the six-course meal, and to go around the table, give everybody the chance to tell us a funny story. As a result "Funny People" is consistently entertaining but also rather grueling -- as if we're watching two or three different movies at the same time. At least one of these -- the tribulations of the young roomies -- we
What is Funny People? Who stars in the film?
film, Seth Rogen
question: What is Funny People?, answer: film, | question: Who stars in the film?, answer: Seth Rogen