A certain sketch-driven shapelessness is a common weakness of many “Saturday Night Live” reunion films. So the smartest thing — of many smart, simultaneously silly things — “Sisters” does is to build in a central setpiece in which manic mugging and scattershot filth are positively de rigueur: the overextended, wildly over-intoxicated house party. Even outside the catastrophe-laden soiree, however, a generally festive spirit runs through writer Paula Pell’s raucous feminization of “Step Brothers,” finally giving the irrepressible Amy Poehler and Tina Fey a big-screen vehicle that feels sympathetically tailored to their comic gifts. If “Pitch Perfect” helmer Jason Moore contributes little in the way of cinematic ingenuity, perhaps he was loath to get in the way of his inspired players: When the laughs flow this freely, a filmmaker’s first responsibility is to keep the camera steady.

Opening on Dec. 18 — thus brashly targeting the demographic for whom “Stars Wars: The Force Awakens” may not necessarily be the most anticipated event of the year — “Sisters” could reap slower but steady benefits from Universal’s counterprogramming strategy in a market not currently over-furnished with grown-up (or at least immaturely adult) laffers. For Poehler, in particular, the pic reps an exciting test of her movie-headliner capability as she pursues pastures beyond “Parks and Recreation.” Irrespective of ultimate B.O. totals, it’s one she aces on screen, gamely carrying an arc that also extends her romantic-comedy credentials past the self-aware irony of last year’s “They Came Together.” Yet as winningly dorky as her romantic rapport is with “The Mindy Project’s” Ike Barinholtz, it’s a mere sideshow to her perfectly synced double act with Fey — a partnership far better served here than it was in 2008’s modestly amusing “Baby Mama.”

Where that film positioned Poehler as the goofball to Fey’s more tightly wound protagonist, “Sisters” puts its leading ladies on a more equal footing, with several narrative reversals cannily shifting the script’s zanier comic demands between them. As the script’s opening beats introduce Atlanta-based chalk-and-cheese siblings Maura (Poehler) and Kate (Fey), it might appear that Poehler has been put on straight-woman duty opposite Fey’s hot mess. A responsible career woman and recent divorcee, Maura is first seen earnestly trying to provide aid to the homeless; that she can’t tell the difference between a hobo and a construction worker, however, hints at farcical reserves of social ineptitude to come. Jobless beautician and single mom Kate, on the other hand, has more immediate problems: Broke, evicted and regarded with weary contempt by her college-age daughter, Haley (Madison Davenport), she resolves to move in with her parents Deanna (Dianne Wiest) and Bucky (James Brolin) in Orlando until her luck picks up.

There’s just one snag: Without warning, Deanna and Bucky have sold the family home in exchange for a compact retirement condo. Charged with clearing out their childhood memorabilia before the new owners move in, their aggrieved daughters — both, it turns out, overly tied to the family apron strings in different ways — are sent into a sulky tailspin. In a fit of pique and misdirected nostalgia, they hit on the least logical course of revenge imaginable: Jointly throw the house party to end all house parties, or at least to halt one house sale.

From that rather basic premise, the ill-conceived bash builds comic momentum via its haphazard invitees, mostly consisting of Maura and Kate’s old high-school classmates — among them John Leguizamo’s skeevy alcoholic, Bobby Moynihan’s desperately clowning perma-nerd and (by force rather than invitation) Maya Rudolph’s hilariously snotty ice queen. As the guest list spirals out of control, so, inevitably, does the event. Outside additions include a hulking, facially tattooed drug dealer (John Cena), a hard-partying troupe of Korean nail-bar workers and an affable neighboring handyman, James (Barinholtz, thoroughly game even as the, er, butt of a key gross-out gag), for whom Maura clumsily has the hots.

Needless to say, whatever can go wrong, does. Moore and editor Lee Haxall crank up to chaos to a fevered breaking point, affording an amped-up ensemble ample room for full-bore hysteria and more incidental moments of comic bliss: Perennial MVP Rudolph, priceless even when standing silent, somehow wrings a tear-inducing laugh simply by name-dropping a D-list celebrity fragrance, while Wiest sells the most inspired streak of on-screen swearing since Armando Iannucci’s “In the Loop.” (Among the lower-billed names, Emily Tarver deserves special commendation for her supremely uninvested retail assistant.) Inevitably, not everything lands, with Moynihan’s extended man-boy shtick perhaps weighing most heavily on a none-too-trim 117-minute running time.

Still, it’s heartening to see energetic supporting players accommodated so generously in a vehicle otherwise decisively steered by its two smashing leads, whose ping-ponging chemistry doesn’t drop for a minute. Even under the ludicrous circumstances, Poehler is oddly touching as a lifelong wallflower finally trying on the debauchery she denied herself in her teens; meanwhile, it’s a treat to see Fey, so practiced in flustered type-A mode, hang loose as a sorely overgrown adolescent being overtaken by her own daughter. Beneath the film’s entertainingly crude hijinks, there are actual human stakes here, as the two sisters recognize in each other the growing up they themselves need to do — though Pell’s script keeps the hugging and learning to a reasonable minimum. In a multiplex landscape still cluttered with manchild-oriented bromances, it’s still all too rare to see belated female coming-of-age given such snappy treatment. (If the definitive female term for “bromance” doesn’t yet exist — sororimance, perhaps? — “Sisters” should prompt its invention.)

Tech credits, a little disappointingly, are on the televisual side: Barry Peterson’s lensing is certainly bright enough, though barring a few establishing aerial shots, the pic (actually shot in New York) makes no attempt to capitalize on its Floridian location. Having the most fun below the line, happily, is costume designer Susan Lyall, whose garment selections are often rich comic punchlines in themselves — not least in a garish mall-makeover sequence that prompts the film’s single wittiest, most all-encapsulating line: “We need a little less Forever 21 and a little more Suddenly 42.”

Film Review: ‘Sisters’

Reviewed at NBC Universal Screening Rooms, London, Dec. 8, 2015. MPAA Rating: R. Running time: 117 MIN.

  • Production: A Universal release of a Little Stranger, Everyman Pictures production. Produced by Tina Fey, Jay Roach, John Lyons. Executive producers, Amy Poehler, Jeff Richmond, Brian Bell. Co-producer, Eric Gurian.
  • Crew: Directed by Jason Moore. Screenplay, Paula Pell. Camera (color, widescreen), Barry Peterson, editor, Lee Haxall; music, Christophe Beck; music supervisors, Julianne Jordan, Julia Michels; production designer, Richard Hoover; art director, Audra Avery; set decorator, Stephanie Bowen; costume designer, Susan Lyall; sound (Dolby Digital), Tom Varga; supervising sound editors, Sean McCormack, Kami Asgar; re-recording mixers, Kevin O'Connell, Bob Beemer; visual effects supervisor, Eric J. Robertson; visual effects, Mr. X Gotham, Factory VFX; stunt coordinator, Victor Paguia; line producer, David Bausch; associate producer, Betsy Rosenbloom, assistant director, Adam Escott; casting, Kerry Bardem, Paul Schnee.
  • With: Amy Poehler, Tina Fey, Ike Barinholtz, Maya Rudolph, Dianne Wiest, James Brolin, Bobby Moynihan, John Cena, Greta Lee, John Leguizamo, Madison Davenport, Rachel Dratch, Santino Fontana, Britt Lower, Kate McKinnon, Samantha Bee, Matt Oberg, Emily Tarver.