When Tina Fey and Amy Poehler lose control together, it’s like that party that was sooo fun but the next day you can’t really explain why. Their latest exploit, “Sisters,” is as loosey-goosey as a movie can get without falling apart, but the amusing twosome’s chemistry mostly overcomes the chaos.

Maura (Poehler) is a divorced nurse and incurable do-gooder, the kind of person who hands out free sunscreen to the homeless and didn’t smoke pot in high school because she was afraid there wouldn’t be enough to go around. Her older sister Kate (Fey) is a wild-child, sporadically employed hairstylist whose own daughter feels like a responsible nerd by comparison.

When their parents (James Brolin and Dianne Wiest) announce via Skype that they’d like to sell the family house in Orlando, the sibs unite to finally clean out their poster-plastered high school bedroom, then plot to sour the deal with the home’s new owners. The only solution, natch, is to throw a debauched, “off the hook” par-tay for all the archetypal losers from high school who are still around, including drunken lech (John Leguizamo), boring mom (Samantha Bee), lame jokester (Bobby Moynihan) and bitter nemesis (Maya Rudolph).

Maura has fallen for another handy nearby archetype — all-American neighbor guy (Ike Barinholtz) — and wants to hook up with him at the party, so the sisters decide to pull a Freaky Friday switcheroo. Maura dons Kate’s daring madcap cloak for the night and Kate plays “party mom,” the one who holds pukers’ hair over the toilet. But when imposing drug dealer Pazuzu (a massively pumped-up John Cena) shows up to peddle his wares, all bets are off. High-jinks ensue, including a ribald sisterly dance-floor butt jam, rock-climbing on the fireplace, make-out sessions, cop drop-ins and vengeful schemes.

“Sisters” is that rare Hollywood comedy that’s actually better than the promo trailers — which had anxious fans fearing the hilarious pair had lost their touch. There’s no story arc to speak of, and the plot is riddled with more holes than an age-inappropriate party dress: No matter how emotionally immature two forty-something women are, can we really expect to believe they’d get so upset over Mom and Dad selling their childhood home? Or that a spontaneous rallying cry from Kate would turn a comatose crowd into 24-hour party people?

No matter. Writer Paula Pell played up the two stars’ strong points in a script tailor-made for them like a sort of haute couture of lowbrow humor. And director Jason Moore (“Pitch Perfect”) has a way with spinning organic gold out of manic “girlfriends night out” energy, bringing in a virtually nonstop cameofest of “SNL” alumni and other familiar funny faces as reinforcement.

Fey and Poehler have never relied more on vulgarity and stretched-out slapstick shtick for easy laughs than they do here. Yet they have no trouble taking the audience along for an LOL ride, because they make you feel like you’re eavesdropping on old friends drinking too much wine at the next table.

No matter what nonsense they spout, their mood is infectious. When Maura tells a doubting Kate that a stunt they’re about to pull is “cool because we’re doing it, and we’re cool,” she may as well be talking about the whole movie. Most people couldn’t induce guffaws by posing under a still of Olivia Newton-John in “Xanadu” while blowing their hair back with an old-school dryer and wearing a frozen, slack-jawed expression. Poehler can, and does.

“Sisters” is no holiday classic, not by a long shot of tequila. But it’s a kick of a way to get your ya-yas out before heading back into the seasonal fray.