It's never really the festive season until you get to hear Mariah belting out everyone's secret and not-so-secret favourite Christmas tune. Mariah joined Jimmy Fallon and his house band The Roots for an acoustic jam session and did what she does best on her classic 'All I Want For Christmas Is You', complete with Fisher Price musical accompaniment. And it's probably one of the best versions of it you'll hear, so stick in the headphones and get Christmasy!