Mariah Carey has been slammed for her "bananas" behaviour when shooting a cameo in 'The House'

Rob said: "We did some reshoots with a pop star named Mariah Carey. It did not go well. F***ing, what is going on with her? It was bananas."

In 'The House' Will Ferrell and Amy Poehler play parents who start an underground casino to fund their daughter's college tuition, and Mariah was cast as herself for a brief appearance.

But according to Rob, although the 47-year-old singer isn't on screen for very long, she wasn't happy with the plotline she was given.

Speaking to SiriusXM's Entertainment Weekly Radio, he said: "She was hired to sing one song, and she was like, 'You guys, I don't want to sing that song.' They're like, 'We hired you to sing this song.'

"So then they were going to do this bit where they shoot her, I think, and they kill her -- in the movie. Not in real life. But she didn't want that. She was like, 'I don't think my character would get killed by bullets. What if I deflected them like Wonder Woman?'

"They were like, 'Mariah, we don't have time for [this]. You're getting paid so much money. We have you for one day. We don't have time to argue with you. Just do it.' She just didn't want to do what they wanted her to do. Anyway, why am I talking trash about her?"

And the 47-year-old actor isn't even sure if Mariah's appearance made the final cut.

Asked if she's still in the film, he said he didn't know and added: "Just know, if you see her, they had to work for it."