Best tweets is a contradiction in terms. Also, get off my lawn, kids!
I would assume that the celebrity tweeters are legit. I know that Gavin Creel's are real, as they've already appeared on his personal twitter.
Relatedly, the official Tony twitter at
http://www.twitter.com/thetonyawards has Mark Indelicato, Betty's nephew on Ugly Betty, as their Tony weekend celebrity tweeter. He might not be one of Broadway's Best (yet), but his "Something's Coming" is fan-freaking-tastic.
"Why, I make more money than... than... than Calvin Coolidge! PUT TOGETHER!"
~Lina Lamont
My name wasn't, isn't, and will never be Scott.