I just finished a book called Sidekicks by Jack D. Ferraiolo , it's based on the young plucky sidekick characters of comic books. In New York, teenager Scott Hutchinson is Bright Boy, the sidekick to Phantom Justice (yes they are a parody of Batman and Robin) who discovers that his arch nemesis, Monkey wrench, sidekick to the nefarious Dr. Chaotic is in fact the most popular kid at school. He suddenly finds himself forced between doing the right thing and being popular at school. Throw in the twist, (which I won't give away) and Scott finds his life really turned upside down!
I gotta say, I found this book really enjoyable. My only problem is that they give away the twist ending by trying to build things up too early. My recommendation, if you want it to really surprise you, skip the black pages. It will really make the climax one hell of a surprise.