LOS ANGELES, CALIFORNIA: Michael Cera has opened up about an incident where Rihanna actually smacked him for real while filming 'This is the End.'

The 2013 comedy movie was about six Los Angeles celebrities who were stuck in James Franco's house after a series of devastating events destroyed the city.

Cera, 35, played a fictionalized version of himself in the film where he was a rude, cocaine-addicted version of the actor and made many enemies, including Rihanna.

At the beginning of the movie at a glamorous house party, Cera’s character slaps the singer, now 35, on the butt.

Rihanna slapped Cera on his face

While on screen slaps are mostly faked in Hollywood, the same cannot be said in case of this movie. While speaking to GQ, Cera admitted that Rihanna did actually hit him and it was a strong blow to his face.

“Yeah, I mean she definitely hit me,” Cera recalled while detailing his role for the outlet. “But I really, I wanted that, you know?"

"I mean, I think it's a lot funnier and a lot more convincing," he said, adding that "a fake slap just doesn't look good.”

According to the actor, the 'Diamonds' singer did not hold back and hit the actor "hard," immediately sending him falling to the floor.

“She really sent me flying, and it was great," he told GQ. “And now it's on film forever, this pain that I experienced."

Seth Rogen also spoke about the slapping incident between Cera and Rihanna

According to People Magazine, Seth Rogen, who was one of the film's co-stars and co-directors, also spoke about the very real slap incident between them on Sway’s Universe just days after 'This Is the End' hit theaters in 2013.

“In the script, Michael Cera slaps Rihanna's ass and she doesn't hit him back,” the actor, 41, told host Sway Calloway at the time.

“But he asked her, ‘Can I slap your ass for real?’ And she said, 'You can slap my ass for real if I can slap you back in the face for real,' ” Rogen said, adding that Cera agreed to her terms.

They did the slap “three or four times,” Rogen said, and on the fourth take, Rihanna “smacked the f*****g s**t” out of Cera.

"She cupped his ear and actually whacked out his equilibrium and he had to go lay down in his trailer for around half an hour," he said.

“That's the take we used in the movie. We didn’t add any sound to that or anything," Rogen added, noting that Cera "was concussed, I think."

Cera encouraged Rihanna to slap him

In a 2013 interview with Rolling Stone, Cera said that he “encouraged” Rihanna to slap him back in the film. “I mean, she hit me hard,” he told the outlet at the time.

“But it was like what it feels like to get hit hard.” He added, "I encouraged her to do it, though. I wanted her to hit me really hard.”