None of the characters are actually new. All of them were introduced in previous sonic games. Big came from the first Sonic Adventure, Cream came from Sonic Advance 2, and Team Chaotix is from the obscure 32X (or was it Saturn?) game Chaotix. Also, Dr. Eggman is his original name. They changed it to Robotnik for the US releases and I guess they just decided to change it back.