“Sisters” is a reminder that we generally love Tina Fey and Amy Poehler for everything except their movies. A sloppy, raunchy, underwritten, poorly assembled mishmash of sentiment and gross-out gags strung along an insultingly thin premise, the comedy still has a few moments that can make you laugh hard enough to shoot soda out your nose. Those moments are largely improvisational, and they reflect not only the stars’ roots in “Saturday Night Live” sketch comedy and half-hour TV shows but the comfort zone of screenwriter Paula Pell — a 20-year “SNL” veteran — and most of the supporting cast. When the new movie wings it, it sputters but clears the runway. When it sticks to the script, it crashes and burns.
The chief novelty lies in letting the stars switch hats, with Fey playing Kate Ellis, a former wild child whose grown-up life is a disaster, and Poehler as Maura, Kate’s uptight nerd of a kid sister. Maura is divorced and closer to her rescue dogs than to other humans, and Kate is living on a friend’s couch, a jobless embarrassment to her levelheaded teen daughter (Madison Davenport).
The two fly to Orlando after learning that their aging parents are selling the childhood home; Dianne Wiest and James Brolin are pretty marvelous as retirees ecstatically divesting themselves of clutter, including their daughters. With mom and dad already in a condo, Kate and Maura decide to have one last shindig before the house passes to its smarmy new owners, so they load up on the booze and send out invitations to all their old high school friends on Facebook.
The bash is the high point of “Sisters” in every sense, and it feels like director Jason Moore (“Pitch Perfect”) told Fey and Poehler to ask everyone in their Contacts app to come over. Bobby Moynihan and Kate McKinnon are on hand from the current iteration of “SNL,” former cast-mates Rachel Dratch and Maya Rudolph play weepy and mean, respectively, and Ike Barinholtz is on loan from “The Mindy Project” as a doughy romantic interest for Maura. John Leguizamo is cast as a sort of walking STD, while muscleman John Cena, so sweetly abused in last summer’s “Trainwreck,” turns out to be this movie’s comic secret weapon as a deadpan drug dealer named Pazuzu.
You’ll find more thought and entertainment in one of Fey and Poehler’s hosting gigs, but when it clicks, “Sisters” feels like a throwback to the early Tom Hanks hit “Bachelor Party,” stopping just short of the cocaine-snorting donkey. The movie does score a few sharp points about how adulthood can dull the edges of even the most relentless teenage party rat, and it staves off the inevitable sisterly argument and sentimental wrap-up as long as possible. Mostly, it’s content to let the stars cuss up a storm and talk in cringe-y “ghetto” slang in a lame attempt to appeal to “the kids” — who will probably go nowhere near this movie except in a pirated version on their laptops.
There is that one scene, though, in which Barinholtz gets a music box playing “Fur Elise” stuck in a most embarrassing place, a bit so filthy and so funny that even Beethoven would have to laugh. With a little more effort, the rest of “Sisters” might meet that high/low bar and live up to the expectations and affection we have for the two comic actresses. But the people responsible for this movie — including Tina Fey and Amy Poehler — clearly believe they only have to show up and schpritz to have a hit on their hands.
The depressing part is that they’re probably right.
Directed by Jason Moore. Written by Paula Pell. Starring Amy Poehler, Tina Fey, Maya Rudolph, Dianne Wiest, James Brolin, John Cena, Ike Barenholtz. At Boston Common, Fenway, suburbs. 118 minutes. R (crude sexual content and language throughout, drug use).