rated R

Weddings invite a certain pressure on all the participants. Every step along the way must be just so, and if even the smallest detail goes awry, all will be ruined.

“Bridesmaids” faces a similar sort of pressure. It’s star and co-writer Kristen Wiig’s first major starring role after toiling for years on “Saturday Night Live” and in bit parts in other movies. What’s more, the film has been pegged as a test case for a new comedy sub-genre, a cross between chick flicks and the raunchy, dude-centric oeuvre of Judd Apatow. But these pressures are ugly and ill-fitting and hide what’s so great about “Bridesmaids”—it’s funny, populated with actual characters, some grand comic set pieces, and a lot of great performances.

Wiig stars as Annie, a down-and-out jewelry store clerk living in Milwaukee. Once upon a time, Annie owned a bakery and had a boyfriend, but the bakery went bust and the boyfriend blew her off. Now she’s working a crappy job, living with a pair of weird roommates, and occasionally sleeping with a handsome, unrepentant jerk (an amusing cameo by John Hamm).

Annie can at least still turn to her best friend Lillian (Maya Rudolph) for help. That is, until Lillian reveals she’s getting married and wants Annie to be her maid of honor. That alone would be enough to drive anyone mad, but Annie soon finds herself in direct competition with Helen (Rose Byrne), another of Lillian’s bridesmaids. Helen is everything Annie isn’t—rich, socially connected, married, glamorous—and the two battle over how to make Lillian’s impending nuptials perfect.

It’s from that battle that director Paul Feig, who created the short-lived but beloved series “Freaks and Geeks,” draws most of the movie’s laughs. Wiig and co-writer Annie Mumolo’s script is close to an endless parade of awkward moments and excruciating faux pas, and Feig always lets those moments go on a beat or two longer than you might expect. “Bridesmaids” works so well because Wiig, Mumolo, and Feig aren’t afraid to let their characters dangle helplessly in those throes of embarrassment.

Wiig is especially good—she’s a great physical comedian, lanky and with a rubbery posture. In one sequence, she gets blasted on scotch and Valium while on a flight to Vegas with the other bridesmaids and proceeds to stumble, slide, and sprint around the plane before she’s taken down.

There are some other, grosser bits, too, reportedly added in by Feig and Apatow, who served as a producer. The ladies venture to a dress fitting after lunch at a seedy-looking Brazilian steakhouse and you can probably guess the final outcome. Even then, though, the characters themselves drive the laughs, like when Wiig, sweating profusely and denying she has food poisoning, defiantly eats a piece of candy to prove her point. There are some slack sequences and a few moments where the movie drags, but Wiig and the cast keep the film going through sheer momentum.

Wiig and Rudolph have an easy, believable chemistry as best friends, and it helps set up the stakes for Annie. The supporting players are great, too. Melissa McCarthy, filling in what would be a Zach Galifianakis role if the gender dynamic were reversed, is terrific as Rudolph’s unceasingly weird, socially awkward sister-in-law. But, unlike Galifianakis, who usually plays his part as a straight freak show, McCarthy’s character is real—she’s got a job, a life, and a full awareness of how strange she can be. Chris O’Dowd, an Irish actor who starred in the British comedy “The IT Crowd,” makes for a surprising romantic interest for Annie, and the other bridesmaids, played by Ellie Kemper and Wendi McLendon-Covey, bring some spark to what could have been forgettable background roles.

Wiig gets to have a major freak-out in the midst of an opulent, Parisian-themed bridal shower. In most movies, that would have been the climax, but in “Bridesmaids,” the mishaps, disasters, and tragedies all resolve through a few well-written, expertly staged conversations.

The laughs in “Bridesmaids” come easy, but the payoffs are well-earned. Perhaps that’s why there’s so much pressure on “Bridesmaids” to be perfect—not because it’s a litmus test for women in modern comedy, but because it’s just a solid, funny film that ever-so-slightly plays against the usual formula. Breaking that sort of traditional mediocrity in a summer comedy is a tough act to pull off, but “Bridesmaids” does it with a mussed-up, go-for-broke elegance.