Mortal Kombat II
To fight Jade, work your way to the match before the mystery fight
(the one titled "?"). During this battle, defeat your opponent using
nothing but low kicks. If you manage this feat you'll fight Jade in
the next battle.
Fight Noob Saibot:
To fight Noob Saibot, get 50 wins in a row.
To fight Smoke, press DOWN + START on the Bridge stage when Dan says
Get 250 fights (the number of battles at versus screen) and a message
will appear transporting you to another dimension. Both players can now
play Pong, who ever wins continues to play.