During the ''Galactic Dancing'' bonus round, don't do anything. You will receive a bonus between 10.000-25.000 points. Hold Up and press Run at the title screen. The capsule on the ship will turn ...

Now just select a game and enjoy! Credit goes to GinsuVictim for posting this on the cheat page for Namco 20 Year Reunion: Ms. Pac-Man/Galaga - Class of 1981.