Easter egg, More Invaders!Edit
There are two secret bonuses on More Invaders!
One, save the very last vertical left column of invaders for last. If you are able to shoot the second one from the bottom last, that nets a 500 point bonus. If you are able to shoot the very bottom invader last, that will grant you a 1000 point bonus.
To unlock the hidden game, on the game select screen, hold down button two on the controller and press button four until the game 23 Matches appears.