“When life gives you lemons, just say ‘Fuck the lemons,’ and bail,” Peter Bretter’s stoner surfing instructor (Paul Rudd) flippantly tells him off the coast of Hawaii as he struggles to get up on his board to ride the waves (of life). Maybe this surfer-bum pseudo-koan is meant to inspire, to provide feelings of hopeful renewal to the film’s hapless center of attention. More likely, it is just another line of vacuous and clichéd dialogue which, like that of the rest of the movie, albeit humorous, fails to leave behind any serious message.

“Forgetting Sarah Marshall” is a funny movie, but one without a purpose. Whether you choose to see it hinges entirely on why you go to the movies.

Bretter, the film’s protagonist, played by Jason Segel who also wrote the film, is the archetypal male of the new genre of films, the dick chick flick (yes, a chick flick for guys), that is the brainchild of Judd Apatow’s production company (of “The 40-Year-Old Virgin,” “Knocked Up” and “Superbad” fame). To put it bluntly, he is a loser: the guy-next-door who lives alone, whose slovenliness is highlighted by his scraggly young beard, poor physical condition, stained sweat pants and diet of Fruit Loops, which he eats out of an industrial aluminum fruit bowl. There is something endearing about his pathetic life — his job as the music player for a CSI-meets-Baywatch TV show, “Crime Scene,” for which his hot, blonde, recent-ex-girlfriend, Sarah Marshall (Kristen Bell) is the star; his dreams of producing a Dracula puppet musical; his penchant for tears, schmaltz, therapy, umbrella-donned curly-cue-straw tropical cocktails and “Project Runway.” He is an antihero, one to whom most twenty-something males will find it easy to relate. And Segel, in by far the strongest performance of the film, plays that role to full effect, with a subtlety and awkwardness that makes him decidedly what an actor of his ilk should be: normal and human.

After Sarah dumps him, Peter decides to get away, to forget his five years of history with her. He arrives at the paradisiacal Turtle Bay Resort on Oahu, Hawaii (“a place where people go to escape the real world”), only to find that his stay won’t be as pleasant as the soft whispers of the ukulele of Israel Kamakawiwo’ole playing in the background. Sarah coincidentally is there as well, with her exotic new rocker boyfriend Aldous Snow (Russel Brand), the creepy British lead singer of Infant Sorrow, whose constant hip gyrations on stage, tight leather pants and floral sarongs, greasy hair and annoyingly dogmatic tendencies create in him a strange mix of Johnny Depp, Gene Simmons and your local tree-hugger. What ensues is predictable: Peter meets a beautiful girl, Rachel Jenson (Mila Kunis), a hotel clerk who walks and talks like a Hawaiian version of Rachel Ray. Rachel’s cutesy, sappy language and nauseating effervescence is hometown-girl-caring but dirtily promiscuous. The two hookup, which inflames jealousy, break-ups and other mindless drama that is the standard fare of romantic-comedies.

The simplistic plot, burdened by this consistent-but-boring acting, is pulled along by comic relief from secondary characters like the surfing instructor and the hotel restaurant host (Jonah Hill). “You’re just by yourself?” Hill bluntly asks Peter when he arrives single to dinner. “Sucks.”

Similarly, the overweight, deceptively intelligent, Hawaiian swami appears in this movie in more than one manifestation to give Peter drinks and advice and to give the audience laughs. But the secondary characters do not coalesce; their hilarious-but-irrelevant jokes and cheesy aphorisms are at times random. It’s like you are at a comedy club with 15-second gigs and in between each act you receive advice from your grandfather.

There is nothing wrong with this orgy of a movie from a perspective of pure, unabashed entertainment. But, as an art, it’s like cotton candy. The screenplay simply does not contain the witticisms that made “40-Year-Old-Virgin” memorable, rather relying too heavily on a bacchanalia of full-frontal nudity, kinky sex jokes and the utterly strange (see the Dracula puppet show scene) to induce a few washed-out gags. See it and you will laugh-out-loud, but then you will, to quote Aldous Snow, “just carr[y] on living [your] life,” and forget it.