The Scorpion King Codes -

Cheat mode:
Highlight the "Continue" option at the main menu, then press Down(2), Right, Up, Right, Up, Right, Down(2), Start. All stages and characters will be unlocked.

Play as Cassandra:
Enter Mathayus, Menmon, Isis, Mathayus as a password to play as Cassandra with all runes.

Level select:
Enter the following character colors at the password screen: Menthu, Isis, Isis, Menthu.