AceShowbiz - Claire Foy freestyled hip-hop classic "Rapper's Delight" during a TV interview on Thursday night, November 29.
However, host Jimmy Fallon surprised Claire at the end of the chat, sharing that he had heard that she knew all the lyrics to the Sugarhill Gang's 1979 hit.
"I heard some weird rumour on the Internet... that you know all the lyrics to 'Rapper's Delight'," he said, to which the 34-year-old replied, "Never trust the Internet!"
A gobsmacked Claire than exclaimed "Oh my God!" as Jimmy handed her a microphone, and she had mere seconds to prepare before house band The Roots launched into the tune.
The star then managed to get through the first three verses of the rap, with the audience offering a huge round of applause, before Jimmy cut to a commercial break.
During the interview, Claire spoke about how much she is looking forward to hosting "Saturday Night Live" on Saturday night, where she will be joined by musical guest Anderson .Paak. And she insisted that she is feeling rather calm about performing in the live show.
"I'm so excited. We don't have it in England, it's not kind of broadcast but I think it's one of those things that is everywhere. you know if there's been a really good sketch because everyone watches it on YouTube," the actress said. "(Everyone is) really lovely, (acting) like I'm supposed to be there and I just feel like a complete imposter. I feel like I should be more nervous than I am - I feel like there's something wrong with me, I'm not having sleepless nights. I'm just sort of going, 'This is fun'. But on Saturday, I'll be like, 'This isn't fun anymore.' This is serious.'"