“The Overnight” opens Friday at Star Cinemas. R, 1:20, three stars out of four.

Making friends with another couple is hard. Even if you like one of them, you might not like the other half as much, and then your spouse has to like both of them. And then each of them, of course, have to like both of you. And then you have to make sure that the other couple isn’t secretly luring you into some sort of “Eyes Wide Shut”-style sexcapade. Because that can get awkward.

Or maybe that last one just applies to Alex and Emily (Adam Scott and Taylor Schilling) in writer-director Patrick Brice’s very funny “The Overnight.” Raunchy and brisk at 80 minutes, “The Overnight” is smart about long-term couplehood, how a marriage defines itself and how it wants to be defined by others.

Alex and Emily have just moved with their young son from Seattle to Los Angeles, and while Emily has settled into her new job, stay-at-home dad Alex is a bit lost at sea, still sporting his Seattle goatee. At the playground, they run into another couple, Kurt (Jason Schwartzman) and Charlotte (Judith Godreche). With his wide-brimmed hat and ironic distaste for Gummi Worms, Kurt is an uber California dad, operating at a level of self-satisfied cool so complete that it looks almost like normal behavior. This is a dad who can put his son to sleep at night with a jazz keyboard solo.

Kurt and Charlotte invite Alex and Emily over for a dinner/playdate combo. The wine and conversation flow, and later the pot, and Alex and Emily are feeling the heady rush of new adult friendship, especially with such a cool yet friendly couple. Sure, there are some weird undertones, like Charlotte insisting on showing the breast pump how-to videos she used to star in, or Kurt showing off his collection of abstract art that look like something anatomically familiar.

Emily starts to get a little wary, but Alex, eager for friendship with Kurt, insists on staying the night. “Maybe this is what dinner parties are like in California,” he reasons. Part of the fun of “The Overnight” is watching for the moment when Alex and Emily should cut bait as things get stranger and stranger — and what happens when, out of a mix of social unease and genuine curiosity, they don’t. Both Schilling (“Orange in the New Black”) and Scott play straight men to the over-the-top Schwartzman and Godreche, Alex and Emily hiding their discomfort under faux hipness. Scott is particularly good at delivering a nervous “Cool, cool, cool,” which telegraphs that things are decidedly uncool.

Even if you think you know where this foursome is going, “The Overnight” has some twists and kinks that may surprise you. The most startling thing, though, may be that in the morning Brice finds an ending for his film that’s rather sweet and wise. Certainly sweeter and wiser than you’d expect from a movie with this many prosthetic penises.