Greenberg; R, 107 minutes; Opening Friday

It’s not writer-director Noah Baumbach’s fault if Greenberg, about a guy named Greenberg, makes me wish for a movie called Zoidberg, about the friendless, incompetent, vaguely Yiddish, attention-craving crustacean physician from “Futurama.” “Oh, it’s all so complicated, with the flowers, and the romance, and the lies upon lies,” Zoidberg once lamented, sounding a note that Greenberg might appreciate. 

Ben Stiller plays Greenberg himself, a man of some 40 years who’s on an aimless quest that would better suit some of the 20somethings he eventually hangs out with.

Except that Greenberg, as played by a perpetually nettled Ben Stiller, doesn’t seem very capable of appreciating anything. Having flown in from New York to skulk around the Los Angeles home of his well-to-do brother (Chris Messina), who has gone abroad, the 40-ish Greenberg promptly embarks on an irresolute affair with his brother’s personal assistant (Greta Gerwig). There is talk of him having just gotten out of the hospital after a nervous breakdown, and, with a similar cautionary tone, of her having just gotten out of a relationship. There is awkward sex. They don’t seem to know what they see in each other, or in themselves. Greenberg keeps touching up his mouth with lip balm, as if to stop it from saying something awful, as if his soul were the thing that’s really chapped.

Baumbach is as perceptive about aimlessness as he is adept at offhandedness. Whether these gifts are ideally complementary may have to remain an open question, even as Greenberg announces that he’s “trying to do nothing for a while”—meanwhile, he still makes time to write cranky letters to companies that have offended him and to brood over his fallow creative ambitions. He used to play music, but now he’s a carpenter. He starts building a doghouse for his brother’s dog, but doesn’t get very far. Greenberg’s way of caring for others tends to consist of inquiring about their opinions of him, with acrimonious forethought. He reconnects with an old flame (Jennifer Jason Leigh, who conceived the story with Baumbach, her husband), and can’t seem to stand seeing her settle in to motherhood. He tracks down an old bandmate (Rhys Ifans), as if only to rehash his reasons for bailing years ago on their record deal. Eventually he finds himself at a house party, feeling threatened by a gaggle of blithe 20somethings and using their coke to embolden his aggression. At one point, while accompanying a woman on her way to have an abortion, the kindest thing he can think to say is, “It’s your day.”

There is bravery in Baumbach’s presentation, but also a sort of self-congratulatory understatement: Baumbach wants us to admire Greenberg because it doesn’t take pains to redeem Greenberg the man. It brings to mind that other willfully, endearingly repulsive character, Zoidberg, who once said, “O.K., so you’re nonchalant. Stop rubbing our noses in it.”