In the sequel to 2014's "Neighbors," the Australian actress portrays a pregnant mom under attack by the sorority that's moved in next-door to her young family. During a scene set at a college tailgate party -- which happens to be one of our all-time favorite scenes in any movie EVER -- Rose's Kelly helps grease up Zac's shirtless alter ego Teddy by rubbing the juices from a slab of meat being grilled during the tailgate onto his buff bod as he prepares to distract the members of Kappa Nu with a steamy strip tease.
But surprisingly, rubbing baby oil onto Zac Efron's toned torso wasn't all it was cracked up to be!
"It was absolutely disgusting," Rose told Wonderwall.com during a press day for "Neighbors 2," which debuts on May 20, 2016.
"We were rubbing pork fat on him," she explains. "It was like a real piece of meat that had been cooked and seasoned in all this oregano and thyme and then it was injected with baby oil to make it really, really greasy."
"The actual stuff was disgusting," she continues. "I couldn't get it off my hands, so we were totally grossed out."
(We're pretty sure that's the first time -- and last! -- that anyone will call touching Zac's buff bod "disgusting.")
Fortunately, it wasn't all a greasy nightmare for Rose, who also called the tailgate scene "hilarious."
"[Director Nick Stoller] kept encouraging us to take it very seriously," the funny-woman told us. "But the more we sat there, the more we started laughing."
In fact, the "Bridesmaid" alum admits that the tailgate scene was one of the hardest for her to get through because she kept breaking character by laughing.
"The more absurd scenes -- like rubbing pork fat on Zac or throwing up on [Seth Rogen] in the middle of a sex scene -- they're just funny," she says.
And, yes, you read that right: Her character throws up on her husband, Seth Rogen's Mac, in the midst of a sex act.
"After being milked [by Seth in 'Neighbors'], really nothing is that bad," Rose says of the hilarious scenes of intimacy she shares with her on-screen hubby. "Everything else is like, you can't really throw anything at me now."
Anything except a slab of baby-oil-infused pork, apparently!