You could, if you wanted, sit in a dark theater and check off the similarities between the blockbuster “Bridesmaids” and this fall’s “Bridesmaids” knockoff, titled “Bachelorette.”

Female bodily function jokes? Check. Inappropriate come-ons on an airline flight? Check. Crass, crude and fearlessly frank talk about sex, once reserved for the fraternity house? Check. Wedding dress disasters? Check.

“My So-Called Life” and “Fast Ties at Ridgemont High” references, singing along with the over-used “I’m Gonna be 500 Miles”? Uh, no. Enthusiastic cocaine snorting, Xanax and alcohol abuse ... wait, say what?

Writer-director Leslye Headland aimed for “Bachelorette” to out-bridesmaid “Bridesmaids.” She’s taken an equally accomplished cast (and a better-looking one) and hurled them at the same heartbreak, fiascoes and emotionally overwrought pathos of an impending wedding, filled their dialogue with F-bombs and amped up their behavior on coke, not the diet kind, either.

And what she’s given us is a romp that never quite romps, a teary-eyed string of taking-stock moments without tears, and a serious squandering of major league movie talent.

The four “B-Faces” have reunited because one of their number is winning that race to the altar, 13 years after graduation.

Kirsten Dunst is icy, cool and bitter as Regan, the 30-something, hyper-organized professional woman, at a loss as to why she hasn’t been the first in her quartet of high school pals to marry. That the dizzy, loose Katie (Isla Fisher) is still single, she understands. Gena (a fierce Lizzy Caplan) has been living a drug-and-booze fueled nightmare since a romantic high school trauma.

And Rebel Wilson of “Bridesmaids” is to be the bride. One of the real rewards of the film is figuring out what connected her to the others.

Regan is in the home stretch of organizing this fete as the maid of honor. But over the weekend of the wedding, we get to see much of her good work come undone.

It’s part reunion movie, part wedding disaster, and both parts are filled with bridesmaids behaving badly.

Headland goes for cheap, broad shocks. And even if the situations are mostly recycled, the words can trigger a laugh. It’s a well-cast film, with Dunst playing against her natural earthy warmth, and Fisher doing the loose-and-dumb thing well. But Caplan is the real breakout here. She lets us see the impulsive mood swings of an addict and manages to keep Gena likable.

It’s another movie aiming to show women who are “Hangover” crude, with a hint of wedding wish-fulfillment fantasy. The transitions from silly to “serious” don’t work. At all. We don’t invest in anybody, so there’s no mourning for the picked-on bride, the wedding or wedding dress that these self-absorbed brats are ruining.

So “Bachelorette” is like the abortive bachelorette party the film trots out, complete with stripper in a scene cut short. It’s a tease for a movie the filmmaker couldn’t deliver.