By the time somebody on screen finally acknowledges that somebody else in “Somebody I Used Know” is doing “some Julia Roberts ‘My Best Friend’s Wedding’ s–t,” we’re already way ahead of her and this movie.

That halfway-mark give-away is amusingly-late and amusingly-obvious in this slightly-raunchier-but-no-edgier riff on the classic “I gotta break up ‘Mister Right’s’ nuptials” rom-com.

That’s the last time I get to use “amusingly” in this review. The film, cooked up by the wife-and-husband team of Allison Brie and Dave Franco, embraces its source material, even mimicking the whole “disrupt a wedding but face no consequences” flaw at the heart of “My Best Friend’s.” It’s just that the laughs are few and far between and the “heart,” so important to a good rom-com, is left out altogether.

The ever-engaging Brie plays a dogged reality TV producer-hostess who has mastered the art of using silence in post-show interview segments to get cast members of “Dessert Island” to weep and confess their heart’s desires and their unhappiness at not achieving them.

Ally has just finished another season of the sex-and-sinfully-good-desserts “contest” series when network brass (Zoe Chao and Sam Richardson) shows up to cancel it. Her agent (Amy Sedaris) is little comfort.

There’s nothing for it but to traipse home, to her single mom (Julie Hagerty) whom she has neglected back in touristy, scenic Leavenworth, Washington, a bit of the Swiss Alps in the Pacific Northwest.

Ally is “Miss Hollywood” to the locals who remember her. It turns out, her ex-beau (Jay Ellis) is one of those who remembers her. And in a big way. A magical night of getting reacquainted ends when Ally stumbles into Sean’s family, getting ready for his wedding.

Damn. No, his “My bad” or its equivalent doesn’t excuse it.

But after chatting up the groom’s caring-but-goofy brother (Brie’s “Community” co-star, Danny Pudi), she starts to think she has a chance, that despite what brother Benny insists, “It’s NOT too late.”

“I need to see this through!”

Kiersey Clemons plays the punk-rocker, non-binary bride-to-be, the one who makes that “My Best Friend’s Wedding” accusation. So, it’s “game on” with each muttering “That bitch” at the other’s moves and counter moves.

The “karaoke scene” from “Wedding” is reprised here as a dare that forces Ally to show everyone her way of rapping/singing DIY songs about a current situation, mentioning by name everybody in that moment with her.

It’s clever and cute — with Brie improvising new lyrics to “Semi-Charmed Kind of Life” by Third Eye Blind — even if it never comes close to the heart-touching delight of that “Wedding” moment. That kind of goes for the entire film.

Haley Joel Osment plays another sibling of Sean’s mostly-adopted family, a married goofball who’s all into dated Hollywood references (“The Office,” etc). He finds a laugh or two, as does Hagerty, playing a mom who has taken a lover and doesn’t interrupt their couplings just because her neglectful, self-absorbed adult daughter is visiting.

Everybody else? A lot of usually funny people are in this, but nobody has anything all that amusing to say or do. Wasting Chao, Richardson and Sedaris this way is a criminal offense.

Even Brie, leaning HARD into a sort of lovelorn-and-clueless Kristen Wiig characterization, has as much trouble finding laughs as she does grabbing hold of the heart of the movie.

The best scenes involve Ally questioning, deceiving and then bonding with Clemons’ “Cassidy.” That’s kind of sweet, but concentrating on that relationship at the expense of your supposed love connection, Sean, is a sign that you’ve pretty much missed the point. Or miscast.

And no, a big nude scene or two doesn’t “patch” this hole in the heart of your romantic comedy.

Rating: R for sexual content, graphic nudity, language throughout and brief drug use.

Cast: Allison Brie, Kiersey Clemens, Jay Ellis, Haley Joel Osment, Julie Hagerty and Danny Pudi.

Credits: Directed by Dave Franco, scripted by Allison Brie and Dave Franco. An Amazon Studios release.

Running time: 1:44