From the game Kid Icarus for the NES.

If you enter the password 8uuuuu uuuuuu uuuuuu uuuuuu you'll start on the final level with invincibility, but there is something strange about this code. First of all, Pit is not visible in the stage intro, although the three treasures are there. Second, the status screen indicates that you have the maximum number of strength arrows, but your bow is actually very weak. Finally, and perhaps strangest of all, the stage loops about 3-4 times before moving on to the boss, Medusa.

Taken with permission from Flying Omelette.