I don't really know who I'd consider my "#1 celeb", to be honest. If authors count, I'd totally choose either J.K. Rowling, Rick Riordan, or Robert Munsch. As for questions, I don't really know, maybe stuff about their books and/or writing process?
The only non-author people I can come up with are Bill Nye (the science guy, who made Gr. 8 science fun), Kelly Clarkson, and Bob the street cat. And yes, I'm referencing a specific Bob the cat...
Actually meeting Bob or Tartar Sauce (Grumpy Cat) would probably be the least nerve-wrecking. Just chill with some awesome kitties!