Enter "Nolan" in any high score table to get an extra game
Flossie's Revenge (at Defender Plus high score table):
Enter "Ovine". Start Defender Plus by pressing A (instead of B).
Warp Enable (at Defender 2000 high score table):
Enter "Beest". During Defender 2000, press 3 to warp to the next level, and
press 6 to warp to the bonus round.
Super Bonus (during Defender 2000):
Catch a falling human as the wave is ending.