Sisters is an uneven mix of raunchy farce and sincerity that's elevated by the undeniable chemistry between Tina Fey and Amy Poehler.

Sisters picks up with high-achieving and upbeat Maura Ellis (Amy Poehler) - who's been divorced for a few years - and her wild-spirited sister Kate (Tina Fey), as the pair head back to their Florida childhood home, only to discover that their parents (Dianne West and James Brolin) have already sold the house and just want the gals to clear out their old bedrooms. While taking this unexpected trip down memory lane, the Ellis sisters wind up deciding to throw one final party at their old home and invite a number of their former high school classmates to join in the fun.

However, what starts out as a decidedly un-hip get together for a pack of grown-ups who are closing in on middle-age soon becomes one wild party to remember, with the sisters leading the charge. The question is, will this "epic" celebration help Maura and Kate to take the next step forward in their lives? Or do the pair just need to be more honest with themselves (and one another), if they're going to get things back on track?

Tina Fey and Amy Poehler haven't co-headlined a film together since Baby Mama in 2008, but in the years since then the pair have only further established themselves as a dynamic comedy duo (see their multiple stints co-hosting the Golden Globes). Sisters leans heavily on their chemistry in order to stay afloat, yet at the same time it gives Fey and Poehler an opportunity to delve into adult comedy material that's too vulgar and risqué for their past television series (30 Rock and Parks and Recreation, in turn). Hence, for devoted fans of the Fey/Poehler pairing, their new big screen venture offers something fresh and different from previous collaborations and solo projects alike; for everyone else, though, Sisters may have more limited appeal.

Sisters unfolds as a semi-farcical take on the high school/college party movie sub-genre, as its various characters squarely fit the common archetypes associated with the sub-genre (the horn-dog, the mean girl, etc.) - despite being twenty or so years older than teen comparisons. The film's observations that adults can easily revert to their juvenile mindsets when given the chance aren't that profound, nor is it always clear if Sisters is parodying the tropes of the average party movie... or just recycling them, with the "twist" being that here 40-somethings are the ones indulging in Project X-style shenanigans rather than people half their age. Sisters has scattershot success with its comedy approach as a result, but on the whole the majority of the film's jokes do hit their mark.

The Sisters script by Paula Pell (a longtime SNL writer) likewise has a loosely-structured narrative that provides room for multiple extended comedy sketches featuring Fey and/or Poehler to unfold (before and during the big party), at the same time that the foundation is laid for dramatic story developments and payoffs in the third act. Sisters' mix of R-Rated irreverent humor and moments of sincere pathos is unbalanced, since Pell proves better at crafting entertaining self-contained scenarios than being able to stitch those skits together to form a solid over-arching through line. Nonetheless, Sisters does manage to create serviceable (if predictable) character arcs for Fey and Poehler's onscreen counterparts.

From a directorial perspective, Jason Moore (Pitch Perfect) stages the proceedings in Sisters in a clean, if unremarkable fashion. There's little in the way of memorable visual comedy during the film's first half since most of the humor is dialogue-driven, but Moore and his cinematographer Barry Peterson (21 & 22 Jump Street) get more creative once the party starts. Sisters feels more cinematic - and less like a glorified TV sitcom - during its second half, as it delivers a greater variety of comedic tones and styles that range from crude slapstick to (intentionally) over the top scenarios and gags. The film's supporting cast plays a key role in this, being composed of several talented comedians who are more than willing to use the film's R-Rating as an excuse to cut loose.

Fey and Poehler are both enjoyable in their Sisters roles - Fey playing against type as the irresponsible Kate, Poehler playing to type (in a good way) as positive-thinking Maura - and carry the movie through its high points as well as low points. However, as mentioned before, Sisters is buoyed by an energetic and engaging supporting roster that includes fellow celebrated SNL veterans Maya Rudolph and Bobby Moynihan in key roles, as well as actors like John Leguizamo (American Ultra) and Ike Barinholtz (The Mindy Project) - with the latter participating in a sweet, but still often (crudely) humorous subplot as a love interest for Poehler.

Some jokes involving side characters in Sisters come off as awkward and fall flat - see those featuring Greta Lee (Wayward Pines) as a nail salon technician for example - while others work better, including those set around Dianne West and James Brolin as the Ellis parents or The Daily Show alum Samantha Bee (as one of Kate and Maura's more pent-up former classmates). Recognizable faces such as Santino Fontana (Crazy Ex-Girlfriend) and Britt Lower (Unforgettable) also pop up, though it's John Cena - as a heavily-tattooed drug dealer - who wins the award for scene-stealing side player, much as he did earlier this year in Trainwreck.

To sum it up: Sisters is an uneven mix of raunchy farce and sincerity that's elevated by the undeniable chemistry between Tina Fey and Amy Poehler. The final film result is a middle of the road comedy that brings to mind many a "party movie" before it (in ways that are both good and bad), yet offers enough variation on that sub-genre's common themes/traditions to avoid being entirely derivative. As a result, Sisters isn't quite the innovative and subversive comedy that it aspires to be, but it's still certainly worth a look for Fey/Poehler fans who are more than game to watch the pair misbehave for a couple of hours (and clearly have fun while doing so).

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Sisters is now playing in U.S. theaters. It is 118 minutes long and is Rated R for crude sexual content and language throughout, and for drug use.

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