Justin Bieber helps out L.A. Reid as a guest mentor on the Oct. 10 episode of 'X Factor' -- Watch a new preview clip below! Bootcamp is over and the top 24 contestants are headed to the judges homes in the new episode, which airs tonight, Oct. 10. Justin Bieber joins judge L.A. Reid as a guest mentor to the delight of the contestants! "They told me that I was too young. You know, you're never too old or too young. If you have the voice and the talent, nothing's impossible," Justin tells the hopefuls. Watch below: [youtube http://www.youtube.com/watch?v=_KPYeovyR-k] Also on tonight's episode, will.i.am helps out Britney Spears, Nick Jonas helps out Demi Lovato, and Marc Anthony joins Simon Cowell. [The X Factor] More X Factor News: ‘X Factor’ Premiere Recap: Demi Lovato & Simon Cowell In Tears ‘X Factor’ Recap: Chris Brown Singer Deangelo Wallace Gets Arrested ‘The X Factor’ Recap: 500-Pound Freddie Combs...