King of Fighters: Dream Match 99 (DC)

Play as Orochi Team:
Press Start on Chris or Yashiro or Shermie in the character selection screen.

Play as Rugal B:
Beat the game once and Press Start on Rugal in the character selection screen.

Clear pause screen:
Pause the game and press X + Y.

Alternate Survival Mode:
Beat Survival mode once. Then highlight the Survival Mode option, hold Start and press A to fight individual characters characters instead of team battles

Teammate assistance:
Hold B when selecting the fighter order before a match. During a round, press X + Y + A when dizzy, and your team-mates will come out and defend you.

Alternate costumes:
Highlight either Andy, Billy, Chris, Joe, Kyo, Mai, Robert, Ryo, Shermie, Terry, Yashiro or Yuri at the character selection screen, then hold Start and press X