The best answer to her son's hardest questions, according to Reese Witherspoon

It's the magical answer to everything!
Actress Reese Witherspoon, who stars in the new animation 'Sing!' had to explain to her four-year-old son how she gets to voice a pig in the movie.
But the idea of his mum playing a pig when she's a human confuses him...
So she told him that it all happens by "magic". And then she realised - this is the answer to give all of her son's hardest questions!
Hear her explain how it happened in the video above.