Very, very few celebrities actively use Twitter, except for the ones who I doubt you would care to get off on. Folks like "Weird Al" Yankovic and Bill Cosby. Most of the more "pop" celebrities (IE, most of the women) either leave their Twitter account to their publicity people, Tweet "at" their followers rather than "to" them, and almost never respond to direct questions - most likely due to the volume of people trying to get their attention.
I have seen some people do what you propose. Their success rate is currently nil. Although, occasionally, you might get lucky... Shelby Cobra (of the pop group KSM) has Tweeted about how ticklish she is on occasion, and there are one or two celebrities (one of whom follows me) who does handle her own Twitter account and actively responds to fans. It's notable, though, because so few actually do.
In other words, don't bother.