Emma Watson showed off her hip-hop skills in a new viral video by beatboxing as Hamilton star Lin-Manuel Miranda spouted a feminist freestyle rap.

The former Harry Potter star and United Nations Women's Global Goodwill Ambassador interviewed the actor/composer as part of the organisation's HeForShe Arts Week, which was set up to encourage arts and cultural organisations to get involved in the fight for gender equality.

While the two discussed everything from the importance of female storytellers to the strong women featured in Lin's Grammy-winning musical, they had a little fun when Emma offered to sort the founding fathers in to the Hogwarts houses from the Harry Potter films.

And the odd couple ended the conversation with the actress asking the fresstyle expert to make up a rap on the spot with the theme of gender equality. Lin only agreed to do so if Emma provided the beats, leaving the actress flustered, and saying, "This is going to be so bad. Do I cover my mouth? This is going to be so embarrassing."

After a few hesitant false starts, Emma finally gave him a respectable beat, as Lin rapped, "Yo, it's Lin and I have to laugh/how can we not be equal, we're like half/like women are like half of the people on Earth/and yes they should've been cut equal since birth. That means equal pay, all day, every way OK/are we really OK? Holy cow this is such a meme/thank you this is the beatbox dream team."

Emma finished with a flushed red face and exclaimed, "I am so embarrassed right now. I'm literally the colour of a tomato. Everyone go see the play and no one ever ask me to beatbox again. These are the lengths I go to for gender equality!"

Lin's freestyle rap is the third he's done in the past week - he rhymed for TV reporter Jenna Bush Hager, the daughter of former President George W. Bush, during an interview for breakfast show Today, and for President Barack Obama during Monday's (14Mar16) cast visit to the White House, where the politician held up signs with random words for Lin to rap.

Lin took to Twitter on Thursday (17Mar16) after the video with Emma was released online and said he was done freestyling for the time being, writing, "Okay, I freestyled for Obama, Bush, and Watson this week. That's a good place to quit while I'm ahead. Future reporters take note."