Simon Cowell was Leona Lewis' mentor on Season 3 of The X Factor UK, and he's Alex & Sierra's mentor on Season 3 of The X Factor USA. What did he have to say about this international collaboration? "You respected the artist. I thought it was a beautiful version. Leona Lewis changed this show forever, and I believe you can change this show forever." Would Alex & Sierra follow in Leona's footsteps and win The X Factor Season 3?