Yes, it is ture and i have them! They are: Metal Sonic - Speed, Dr. Eggman - Fly (because of his machine), and (i would have never guessed this) Chaos - Power. Their missions are VERY hard and are only fighting against the other teams! The way to get them is collect all emblems, emeralds and complete every second mission on eaach stage. It took me a year but it was SO worth it!