When you are fighting at the Portal Stage in a 1 or 2-Player game you can fight Smoke at Goro's Lair when Dan Forden appears at the bottom of the screen and yells 'Toasty!' and you hold Down and Start at the same time immediately he appears. Note: Dan Forden only appears randomly after an uppercut.
When you reach the match that is before the '?' on the match chart you can fight Jade at Goro's Lair if one of the rounds is won using only Low Kicks and the Directional Pad. The other round can be won normally.
The following code will only work on the WaveNet edition of the game. Before you enter the code you must be playing against another human opponent and immediately before round 1 starts hold Back + Low Punch + Low Kick + High Punch + Block. If you have entered the code correctly the human character you selected will explode into Noob Saibot.