LAS VEGAS − The “Spa Weekend” filmmakers have a bit of life advice.

“We hate goats,” says Jon Lucas, making his co-director and screenwriting partner Scott Moore laugh. “Don’t ever work with goats.”

The duo behind beloved comedies such as “The Hangover” and “Bad Moms” have writers’ regret about a scene in their new farce, arriving in theaters Aug. 21. In “Spa Weekend,” a longstanding group of friends − played by Michelle Buteau, Anna Faris, Isla Fisher and Leslie Mann − try out goat yoga while staying at a resort, where they reconnect and recuperate from their busy lives.

“We didn’t have any CGI goats,” Moore reveals. “They’re all real goats.”

Fisher, 50, says this scene was the most challenging to film, thanks to her unpredictable, four-legged costars.

“It was as if the goats had never seen humans before. They were pooping and peeing and screaming,” she said at the movie’s world premiere at Fontainebleau Las Vegas. “I was happy when that scene was over.”

For research, producer Suzanne Todd attended a goat yoga class, “which was terrifying and smelly and hard, really hard!”

“We went into it thinking it was going to be this magical goat thing,” Todd says, predicting the goats would intuitively apply a bit of pressure at the appropriate time, like an instructor. “None of that from the goats, none at all!

“When they would stand on your back, it’s actually really hard because the goat is heavy, and those hooves are sharp!”

Moore remembers Mann handling the goats like a champion, while clad in only yoga attire.

“It was her bare back with these hooves,” he says. “And every time I’m like, ‘Oh, my God. We’re scratching up her back.’ Leslie did not complain. She was just in it.”

Mann, 54, smiles while recalling the experience at the premiere, where she wore a strapless, vintage gown embellished with stones.

“The goats were a lot older than they said they were going to be, so they were large, like full-grown goats,” Mann says. They “liked to climb on our backs, and I was scratched up and bruised, but it was fun.”

Injuries are nothing new for the leading ladies, who have “all been in the world of comedy for so long,” Faris says in an interview with her costars.

 “I remember in ‘George of the Jungle,’ being in a scene with a lion!” Mann says, astonishing her costars.  

In the 1997 film, the title character (Brendan Fraser) tussles with the beast before rescuing Ursula (Mann). The actress says the lion wasn’t sedated and had a “trainer guy off to the side. But the lion could reach me before the trainer guy could” intervene.

“Leslie, I feel that experience,” Faris, 49, says, “because doing those ‘Scary Movies,’ early on, back in the day, it was like, ‘Oh, they don’t mind if I drown? Uh, OK.’ ”