Starting with Chicago’s ImprovOlympic in the early 1990s and continuing through “Saturday Night Live” and films and even hosting the Golden Globes with terrific style, Tina Fey and Amy Poehler have been arguably the funniest, smartest, most entertaining comedic duo of the last quarter-century.

Not to mention their stellar individual achievements, most notably Fey’s “30 Rock” and Poehler’s “Parks and Recreation.” Year after year, as solo talents and a team, they’ve been knocking it out of the park. I think they’re great and I’ll bet you do as well.

So it’s with no small reluctance I report “Sisters” is a depressing, overlong, repetitive slapstick disaster in which two of the most appealing stars around wallow in the muck AND the mire, figuratively and literally.

Given the screenplay is by longtime “Saturday Night Live” scribe Paula Pell and the director is Jason Moore (“Pitch Perfect”), it’s genuinely surprising that “Sisters” reaches for such low-hanging fruit.

If your idea of cutting-edge humor is a drugged-out, fortysomething class clown doing artwork with his genitals; a pratfall that results in a musical ballerina figurine jammed up a man’s rear end; tired stereotypes about lesbians and Korean manicurists; numerous characters making drunken fools of themselves and, yes, sisters wrestling in mud, by all means step right up and purchase a ticket.

Fey plays Kate, an irresponsible and unlikable (she calls herself “brassy”) mother of a teenage daughter (Madison Davenport). The girl is understandably embarrassed by her mother’s inability to hold down a job or maintain a steady home. Poehler is Kate’s younger sister Maura, a nurse who spends nearly every waking minute helping others, whether they ask for it or not.

When Maura learns their parents (James Brolin and Dianne Wiest, trying hard) are selling the family home in Orlando, she and Kate race to Florida — only to find a “SOLD” sign planted in the lawn, Mom and Dad already living in a condo in a senior citizens’ complex, and a nearly empty house save for their two bedrooms, which apparently haven’t been touched since the girls moved out — when, 20 years ago??

That’s the setup. The bulk of the movie is the party thrown by Kate and Maura in their beloved childhood home — but for once, Kate will be the non-drinking “mom” who looks after everyone else, and Maura will let her freak flag fly.

The sisters round up the old high school gang, most of them now married with children and long past their partying days.

Maya Rudolph is Brinda, Kate’s longtime nemesis. (When we find out why they can’t stand each other, it’s Kate who comes off poorly.)

Bobby Moynihan is Alex, a supremely unfunny guy who tells horrible jokes and seems unaware that nobody likes him.

John Leguizamo is Dave, a cheerful loser apparently still stuck in 1989.

Rachel Dratch is Kelly, who’s depressed because time is marching on and she feels old.

Gee, what a fun bunch.

Ike Barinholtz lends his easy charm to the part of James, a nice guy from down the street who becomes a romantic interest for Maura. (The scene in which Maura and Kate meet James as he’s landscaping in his front yard and they flirt with him is so tone-dead, and the sisters come off as so obnoxious, it’s a wonder this guy shows up for their party.)

Fueled by drugs and booze, dozens of fortysomethings raise the roof and then tear the roof down. In scene after scene after scene after — well, you get the idea, these middle-aged maniacs abuse the house and the surrounding grounds in mind-numbingly uncreative fashion.

Poehler and Fey seem to be having fun sexing it up a bit, wearing provocative clothing and performing dance numbers and flaunting their attractiveness more than is their usual practice. Even though they look nothing like sisters, they’re believable as sisters. Every once in a while when we take a break from the thuddingly unfunny slapstick stuff, there’s a nice and genuine moment.

But then we’re back in the mud.

And the mire.

[s3r star=1.5/4]

Universal Pictures presents a film directed by Jason Moore and written by Paula Pell. Running time: 118 minutes. Rated R (for crude sexual content and language throughout, and for drug use). Opens Friday at local theaters.