If you had the chance to interview any celebrity, who would it be and what would you ask them?

This is not strictly a what-if question. I have actually been given the permission by a teen magazine to interview the celebrity of my choice. I need some ideas! Part of me wants to interview a musician like Vanessa Carlton or Michelle Branch but another part of me knows I need to interview someone the majority of people recognize... It can be anyone from Laura Bush to Dana Carvey to Zac Efron.