Play as Smoke
  At the title screen press UP, UP, LEFT, RIGHT, A, B, A, B, UP, DOWN, UP. If
  done correctly, you should hear "Toasty!" Now pick Rayden, and Smoke shall be
  at your control!

Play as Gore
  Finish the whole game with any fighter. Wait for the credits and the words
  "The End" to appear. Simultaneously press and hold UP + LEFT, SELECT and A
  until the Title screen appears. Release all buttons, and press START to play
  as Goro.