Unlock arena mode, then press Start, Down, Up, Down, Up, Right(2), Left(2), Right, Down, Select at the map screen.
Bonus characters
Defeat the following characters in arena mode to unlock them as playable characters: Aburame Shino, Akimichi Chouji, Dosu Kinuta, Gaara, Haku, Hatake Kakashi, Hyuuga Hinata, Hyuuga Neji, Inuzuka Kiba, Kankurou, Kin Tsuchi, Momochi Zabuza, Nara Shikamaru, Rock Lee, Temari, TenTen, Yamanaka Ino, and Zaku Abumi.
