"Fifty Shades of Grey" cast Rita Ora had swapped her blond locks to play Christian Grey's sister in the highly anticipated film. Calvin Harris' ex even promised that the movie will make a lot of waves when it opens in time for Valentine's Day next year.

New still released by the studio showed singer Rita Ora sporting brunette bob for "Fifty Shades of Grey."

"And just in time for her 24th birthday, Rita Ora was given a special birthday shout out on Wednesday along with the first photo of her character Mia who sports a brunette bob in the film," said MailOnline. "Described as 'Christian's lively and vivacious little sister,' Rita transformed into Mia Grey by swapping her platinum locks for a darker and much shorter hairdo."

Rita Ora is shown dressed in a rather bland floral top with dangling earrings, which is a stark contrast to her outrageous outfits, and Christian Grey's sharp suits.

The singer will play a very small role in the film but it's her first acting gig, which is why she's very excited. Calvin Harris' ex even added that she caught the acting bug.

"I have the bug, for real. Fifty Shades was a moment of cameo and a really good wake-up call. It was nice to be a part of it and it opened a lot of doors," she told OK! Magazine.

"For me this was such a great cameo to be involved in, and even though I'm only in it for a little bit, it's opened the door to a lot of movie things that I haven't actually announced yet," she said. "Fifty Shades is going to make a lot of waves, I'll tell you that much. It's going to be awesome."

"Fifty Shades of Grey" cast Rita Ora actually approached the producers so she could take part in the movie's soundtrack. But the director Sam Taylor-Johnson auditioned her for the part of Mia Grey instead.