Just beat the main game 100%, including all hidden characters in chaos, all crossover trophies and all chaos challenges completed (not including christmas challenge, or any future updates) and just message me on Twitter!
Okay, Thx! :D
So far for the Hidden Characters in Chaos I've found Zipper and the HOW2PLAYROCKRADIO.
Edit: I have all the Secret Char. I am working on the challenge! :D