Press and hold the SELECT button while choosing your character. Continue holding the SELECT button down until the match begins and your character will have a bigger head. For an even bigger head, win a match in bug head mode and then begin holding down the SELECT button during your victory pose. Keep holding the SELECT button throughout the character selection preocess until the next match begins. (Note: You must have beaten all of the sub-bosses to use this code. See other code for clues on how to get Roger/Alex.)
After you have obtained all the sub-bosses, and have beat Devil Kazuya, start a new game in Arcade Mode using Heihachi. When you get to your third match, let your opponent beat you down to 5% energy. Now comeback and knock out your opponent. If you've done this correctly, the announcer will say 'Great!' Your fourth match will be against Roger/Alex. Beat him and the next six matches and you will be able to play as Roger/Alex.
Hold down the L1 and L2 buttons while selecting a character. Keep holding the L1 and L2 buttons until the matcg begins. Not only will your character appear as a green wire frame, the perspective will be from behind your character, looking through them!