Margot Robbie was left shocked when her brother turned up to interview her about her new movie 'Peter Rabbit'.

The 27-year-old actress is busy promoting the children's film in her native Australia, and the 'I, Tonya' star was given a surprise when she was getting ready to talk about the project - based on Beatrix Potter's books - only for her 23-year-old sibling Cameron to arrive to quiz her for MTV Australia.

In the hilarious moment caught on camera, Margot - who grew up on the Gold Coast hinterland - sits down with her co-star Elizabeth Debicki to do some promo when Cameron makes his appearance.

The blonde beauty exclaimed: ''Oh my God! What are you doing?! What are you doing?! What is going on right now?! This is so crazy. You're an interviewer on MTV.''

But her playful brother quipped: ''Excuse me, this is a professional situation. Can you just calm down?''

Margot voices Peter Rabbit's sister Flopsy in the animated film alongside James Corden who brings the titular character to life, and Cameron teased that there were similarities between the ''dim-witted'' rabbit and his older sister.

He said: ''It's funny, in the film I noticed a lot of real life correlations between the character Flopsy [and you]. She seems quite, you know at times airy and dim-witted. Do you think that was intentional casting? I just thought there was a nice correlation between you two.''

But Margot - who, along with Cameron, also has older brother Lachlan and sister Anya -retorted: ''It's funny that's what you took from it, I thought she was maybe insecure and unheard perhaps amongst her siblings. No? Didn't come across that way?''

The duo aren't strangers to sibling banter, as Cameron gave Margot a hard time after losing out on the Best Actress Oscar to Frances McDormand at this year's Academy Awards.

He posted on his Instagram Story: ''Not good enough are ya #imstillmumsfavouriteiguess,''

But he followed up with a more sentimental post: ''Just kidding. I'm literally crying right here. Not a dry eye in the house.''