King of Fighters 2003 cheat codes

Fight as Adelheid:
In arcade mode, reach Kusanagi and defeat him with a normal move. Then, defeat Adelheid in the final Boss battle. Next, highlight Iori at the character selection screen and hold R.

Fight as Mukai:
In arcade mode, reach Kusanagi and defeat him using a DM move. Then, defeat Mukai in the final Boss battle. Next, highlight Kyo at the character selection screen and hold R.

Gallery items:
Win one round of S-Survival single mode against each character to unlock individual character art in the gallery menu.

Win one round of T-Survival team mode against each team to unlock the team ending sequences in the gallery. Note: Defeating Kyo, Chizuru, Adel and Mukai will unlock the usual intermission sequences that occur before and after fighting them.