When the media labeled 2011's alternately hilarious, heartfelt "Bridesmaids" as a female version of 2009's "The Hangover," it came as a lazy and sexist retort that insulted just how very good the Kristen Wiig-starring "Bridesmaids" was while giving the rancid, mean-spirited raunchfest that was "The Hangover" far more credit than it deserved. If one were to go by subject matter alone, dark, brazenly uninhibited farce "Bachelorette" invites a closer comparison to "The Hangover," albeit, once again, with a level of intelligence and wit that the latter low-rent Todd Phillips film could never lay claim to (and let's not even mention its even-worse 2011 sequel, "The Hangover Part II"). Armed with four almost scarily terrific performances from Kirsten Dunst (2011's "Melancholia"), Lizzy Caplan (2010's "Hot Tub Time Machine"), Isla Fisher (2009's "Confessions of a Shopaholic"), and Rebel Wilson (2012's "What to Expect When You're Expecting"), this drug-fueled, up-all-night comedy of errors, written and directed by Leslye Headland (based on her play), isn't afraid to be thematically ugly or profane. Even as one laughs, however, there is a sadness beneath the humor, an unexpected compassionate side that flinches at the frequently unsavory sight of its protagonists and wonders how they got that way. There is always the possibility to change for the better, but said adjustments, as in real life, are likely to come in slow bubbles rather than large bursts. Don't expect anyone to be a completely different person overnight, because it's not going to happen.

They haven't been in high school since 1999, but the high-strung, Type-A Regan (Kirsten Dunst) prides herself on remaining the queen bee of her inner circle quartet that also includes loose, acerbic party girl Gena (Lizzy Caplan), terminally ditzy retail salesgirl Katie (Isla Fisher), and comparatively well-adjusted, overweight Becky (Rebel Wilson). Regan always assumed she'd be the first to walk down the aisle—a dream that goes kablooey when she discovers Becky has gotten engaged to Dale (Hayes MacArthur). Regan is mortified, but shields her feelings as she jumps into the position of Becky's maid of honor, working with the wedding planner to ensure everything goes off without a hitch while also spearheading a low-key bachelorette party. Gena and Katie excitedly reunite with Regan and Becky the night before the nuptials, but things quickly go downhill. The stripper, a former classmate, cruelly calls Becky her teenage nickname, "Pigface," successfully ending the celebration. Even worse, the girls rip Becky's wedding dress when they try to get in it together. High and drunk and God only knows what else, Regan, Katie and Gena set out into the Manhattan night in search of a way to mend the dress and return it before Becky finds out. Along the way, they are faced with some harsh reminders of their past and a few much-needed wake-up calls.

In "Bachelorette," the central characters are thirteen years removed from high school, and very little has changed in that time. It's an epiphany that's been a long time coming for the self-involved likes of Regan, Gena and Katie, the three of them stuck in a mental time warp that has stalled their growth into adulthood. Sure, Regan prides herself on working with children with cancer, but she is just as fast to turn around and mourn the thought of getting a disease at the exact age when girls start to hate themselves. At lunch, Regan prattles on about herself, barely allowing Becky to get a word in edgewise—that is, until she announces her engagement. They're supposed to be best friends, but Regan has mostly kept the chubby Becky around to help her feel better about herself. Now, for the first time, she's inadvertently made her feel worse. That Becky's a genuinely kind and caring person likely doesn't even show up as a blip on Regan's radar. As for Gena, she's now an L.A. native, used to partying hard and waking up in strange guys' beds. Katie is very similar, recreationally into drugs enough that she nearly overdoses every weekend, but also dumber, mourning her inability to understand half the things that come out of people's mouths. The thought of reuniting with her old friends for the weekend is almost too much for Katie to handle. "I'm so excited I could buy a gun!" she exclaims upon arrival at the hotel.

First-time writer-director Leslye Headland doesn't hold back, never afraid to show the sometimes competitive nature of friendship and the off-putting sides of people's personalities. Watching Regan, Gena and Katie, the viewer isn't sure he or she likes them at all, then pretty much confirms that they deserve whatever bad stuff's coming to them. All the same, they are ridiculously entertaining in their conceited ways, and not unredeemable. Regan comes to feel mighty bad about how poorly she's treated Becky (even if a lot of it has been behind her back), and isn't sure how she's going to fix her current predicament. There are also some more serious things going on with her that won't be revealed. Gena comes face-to-face with her high school ex, Clyde (Adam Scott), his appearance rattling up all kinds of memories she'd like to forget. Having grown accustomed to dulling her pain with cocaine and alcohol, Gena is stung by her own arrested development when Clyde sternly tells her, "It's not cute anymore." And then there's Katie, who might be the most tragic of them all, blissfully going through her days with nothing to fill her head with but air. Is she really that dumb, though, or is she always so high that it's simply difficult to think straight? When a nice guy from her past, Joe (Kyle Bornheimer), shows interest in her that goes beyond sexual attraction, Katie doesn't know how to deal with it. She's never had someone like her for who she is before.

The performances are ripe with an inspiration only equalled by the sharp pin-point writing. Kirsten Dunst leads the way, playing against type as the shrill and acid-tongued Regan, amazingly efficient in her ability to control a situation that is falling apart around her. A climactic scene where Regan must contend with an unhappy bride, an incorrect floral arrangement, a missing wedding dress, a guy incessantly banging on a door in the other room, and a friend who has overdosed in the bathroom is a zonky example of screwball comedy at its best. As Gena, the deliciously snappy Lizzy Caplan is dealt the biggest arc; she is the most self-aware of how far she's allowed her life to go astray, and the actress turns in work that is at once very funny and surprisingly poignant. Like Caplan, Isla Fisher is a master of comedic delivery, and she earns some of the biggest laughs. Slyly but surely, Fisher transforms Katie from a resident idiot into a decidedly complex individual, lovable in her lack of tact and meaning well even when she's screwing up. Finally, Rebel Wilson gives the most humane performance of her career so far, a chance to prove that she is capable of so much more than she's been given credit for. Often treated as the supporting comic relief or punchline, Wilson has drawn a deft and touching portrait out of Becky, a young woman far smarter than her friends give her credit for who learns, little by little, how to stand up for herself. It is mighty refreshing to also see that Becky and her handsome groom are wholly committed and genuinely love each other; there is no ulterior motive going on, despite what some people pettily suspect.

"Bachelorette" pushes a little too hard for a happy, moralistic ending that only cursorily convinces, but the getting-there is such a trip that it matters less in the long run if certain story threads are left dangling. The full ensemble are a treat to see play off one another, while the narrative moves at such a snappy rate not a single scene threatens to wear out its welcome. Laughs are plentiful, even with some of them flying under the radar and easy to miss, while references to yesterday's pop-culture ("My So-Called Life" plays a major part in one conversation) exhibits how learned and in-tune Leslye Headland is with the ages of her characters. When Regan finally drops her defenses near the end and shows emotion, Gena's reaction—"You haven't cried since Thomas J died in 'My Girl'!"—is at once supremely amusing and truthful. So, too, are the soundtrack cues, many of them harking back to a specific time in the '90s that subtly shed light on these girls' past without needing to spell anything out. The use of The Proclaimer's "I'm Gonna Be (500 Miles)" and Goo Goo Dolls' "Slide" are especially succinct. Fiercely independent-minded while retaining an up-tempo, mainstream pace, "Bachelorette" is as black as comedy can get while still ending up a crowd-pleaser. Straddling a very fine line, but never toppling over, the film's future cult status and high rewatchability factor are all but guaranteed.