At the Lucas Arts logo, press Up + A, Down + A, Left + A, Right + A until you hear a tone (several times). To activate, press C while playing to skip a level.
Password - Effect:
DERLIN - Easy: Asteroid Field
BOSSK - Easy: Beggar's Canyon
LIANNA - Easy: Cannon
ENGRET - Easy: Canyon Asteroid
RALRRA - Easy: Canyon Run
KLAATU - Easy: Death Star
IRENEZ - Easy: Death Star Surface
MOLTOK - Easy: Imperial Walkers
PAKKA - Easy: Power Relay
FRIJA - Easy: Star Destroyer
MORAG - Easy: Storm Troopers
LARFRA - Easy: Tatoonie Attack
TANTISS - Easy: Transport
NORVAC - Easy: Trench Run
OSWAFL - Easy: Yavin Training
TARKIN - Hard: Asteroid Field
BORDOK - Hard: Beggar's Canyon
VONZEL - Hard: Cannon
SKYNX - Hard: Canyon Asteroid
DEFEL - Hard: Canyon Run
IZRINA - Hard: Death Star
KARRDE - Hard: Death Star Surface
MOTHMA - Hard: Imperial Walkers
OSSUS - Hard: Power Relay
JEDGAR - Hard: Star Destroyer
GLAYYD - Hard: Storm Troopers
MADINE - Hard: Tatoonie Attack
OTTEGA - Hard: Transport
MALANI - Hard: Trench Run
RISHII - Hard: Yavin Training
MAZZIC - Normal: Asteroid Field
BOTHAN - Normal: Beggar's Canyon
UMWAK - Normal: Cannon
HERGLIC - Normal: Canyon Asteroid
LEENI - Normal: Canyon Run
JHOFF - Normal: Death Star
ITHOR - Normal: Death Star Surface
JULPA - Normal: Imperial Walkers
ORLOK - Normal: Power Relay
THRAWN - Normal: Star Destroyer
MORRT - Normal: Storm Troopers
LWYLL - Normal: Tatoonie Attack
MUFTAK - Normal: Transport
NKLLON - Normal: Trench Run
RASKAR - Normal: Yavin Training