There are two kinds of people in the world. Those who think that the sight of a man's personal parts in a movie is hilarious. And those who think that for those personal parts or anything else to be funny, they have to be associated with some kind of joke.

The first kind of people, and their numbers are growing, are the sort who flock to Judd Apatow movies.

They aren't looking for what used to be the staples of humor: wit, cleverness, surprise, unpredictability or absurdity. All they ask is for people to go through the motions of being funny, to effect an attitude of being funny.

It's so much easier that way. You don't even have to come up with interesting characters or a story.

Which is why "Forgetting Sarah Marshall" will draw crowds. People who don't care about characters or a story will love it. Especially if they laugh for no reason at male nudity.

Jason Segel stars as Peter, a composer whose actress girlfriend dumps him (the scene is the first time we see his anatomy, but not the last. And it doesn't get any funnier as the film goes along).

Upset, Peter first tries to forget Sarah Marshall (Kristin Bell) by sleeping with a series of women. Then he goes on vacation to Hawaii, where he runs into the ex and her new boyfriend. So he consoles himself with the attentions of the equally beautiful hotel clerk (Mila Kunis).

What she sees in him is anyone's guess. Segel, who wrote the script, did not give his main character any personality whatsoever. None. Nor did he yield to the impulse to bestow a personality on the ex-girlfriend, Sarah Marshall.

The hotel clerk shows the tiniest bit of a personality near the end, which makes her way more fascinating than anyone else in the picture, even though she suffers some weird sort of psychotic break when she encounters her own ex-boyfriend earlier in the film.

It's the laziest sort of writing for Segel, who makes his debut as a writer. Not only does he not bother to give any character to his characters, he doesn't condescend to create a story for them. And rather than think of a way to drive them together, he simply has them run into one another.

Peter goes to Hawaii and he runs into Sarah. He checks into a hotel and he runs into Sarah. He walks down the path and he sees Sarah and her boyfriend. He goes to a bar and he runs into them. He goes to a restaurant and he runs into them. He goes to a restaurant again and he runs into them again. He goes to a luau and he runs into them. He goes to a bar again and he runs into them again. He goes surfing and he runs into the boyfriend on the waves. He goes into the hotel lobby and he runs into the boyfriend again.

They must be on one of Hawaii's smallest islands, inhabited by perhaps a total of six people who run into one another constantly.

Nicholas Stoller makes an equally undistinguished debut as a director. He, too, has picked up on the whole you-don't-have-to-try-hard vibe and seems to have worked with none of the performers on their acting. Nor has he stressed the importance of enunciation; a good chunk of the dialogue is impossible to understand.

For the record, I did laugh once, at a slyly vulgar joke about a necklace. And there is a spate of about five minutes, beginning with the last time they all meet in the restaurant, that is atypically not unamusing.

But for the most part, no one will have a hard time forgetting "Forgetting Sarah Marshall."