Paul Rudd and Amy Poehler star in "They Came Together," a parody of romantic comedies from writers David Wain and Michael Showalter. The Post's Ann Hornaday gives an annotated review of the film. (Jayne W. Orenstein/The Washington Post)

Perhaps all you need to know about “They Came Together” is that the team that wrote and directed “Wet, Hot American Summer” brought it to the screen. Larky, witty and sometimes even wise, this spoof on every rom-com ever made is less a fully realized film than an extended skit, a series of set pieces that poke gentle and sometimes transgressively crude fun at the tropes of girl-meets-boy that have enchanted and addled audiences for generations.

Trotting out each genre convention only to take the mickey out of them with vivisectionist glee, “They Came Together” winds up being oddly cathartic: It awakens the audience from its lingering Nora Ephron-induced coma with a splash of cold water delivered straight from a clown’s boutonniere.

“They Came Together” opens with two couples enjoying dinner, during which they exchange stories about how they met. Soon enough, Molly (Amy Poehler) and Joel (Paul Rudd) are regaling their glaze-eyed friends (Bill Hader and Ellie Kemper) about how they got together “in a corny, romantic-comedy kind of way,” with Joel dutifully taking the role of handsome-but-not-threatening leading man who’s “just Jewish enough” and Molly being the “cute, klutzy” girl whose lack of coordination leads to all kinds of adorkable mishaps.

In “They Came Together,” that includes falling down an entire flight of stairs, before going to her picture-perfect job at a quirky, “impossible not to like” candy shop on the Upper West Side where all proceeds go to charity and where, unbeknownst to her, she’s the target of a mega-competitor’s plot to put her out of business. You don’t need to have watched “You’ve Got Mail” 100 times — preferably in your pajamas, with a pint of Haagen-Dazs and the phone off the hook — to know that the corporate drone behind impending doom is none other than Joel, whom she meets at a Halloween party where they’ve both arrived dressed as Benjamin Franklin. It’s that scene to which the title refers — another little subversion of expectations at which the film gleefully excels.

The meet-cute, the inevitable breakup and all the de rigueur montages are included in “They Came Together,” which casts all the way back to “Crossing Delancey” for satirical inspiration (and perhaps the movie’s most breathtakingly tasteless scene). Written by David Wain and Michael Showalter and directed by Wain, this silly, slight, sunny homage to the Hollywood mainstream at its most ersatz and ingratiating features a slew of memorable sequences, including a time loop set at a neighborhood bar in which the phrases “Tell me about it” and “You can say that again” take on the classic hilarity of this century’s “Who’s on first.” One of the film’s several running gags centers on the rom-com staple of stopping people just before they leave with a soft “Hey” and, when they turn around, saying an equally soft and sincere “Thanks.”

“They Came Together” is anything but subtle, and the film’s tendency to put quotation marks around everything would easily grow as tiresome as the hackneyed cliches were it not for Poehler and Rudd, each of whom plays it utterly straight. (As usual, Rudd is particularly sensational in a role that asks him to be coarsely profane and wholesomely boyish in the same breath, a feat perhaps only he could pull off.) Helped along by supporting players Ed Helms and Christopher Meloni (featured in the film’s most amusing scatological gag), as well as a raft of choice cameo appearances, Rudd and Poehler keep “They Came Together” floating along on a cloud of barely winking humor and their characters’ shared love of “fiction books,” Q-tips and coffee. “Who are you?” they keep asking each other, amazed at the banalities they have in common.

The answer, of course, is that they’re Harry and Sally and Sam and Annie and Sam and Isabelle and, finally, Joel and Molly — all wrapped into one cute, klutzy, vaguely ethnic package. And despite “They Came Together’s” alternately obvious and observant efforts to send them up, they’re impossible not to like.

★ ★ ½

R. At AFI Silver and West End Cinema. Contains profanity and sexual content. 83 minutes.