Duck Hunt: Level 100 error

In the game Duck Hunt for NES, after you pass level 99, the game will reach a glitched level.

How to activate
Beat level 99 and you will access level "0", which is a glitch level. It may be long and hard to get to this level, so don't try if you know you can't get there! If you somehow manage to beat this game (using cheat codes), you will return to level 1.

What happens?
Here are some, but not all of the problems encountered in level 0.
 * The ducks move at an extremely fast speed, making it almost impossible to hit them.


 * The dog randomly laughs at you, making you lose a bird without doing a thing!


 * Unless you get extremely lucky and hit every duck, you will probably lose.

Credits

 * raydempsey and his video on YouTube

Links
http://www.youtube.com/watch?v=AjUpe7Oh1j0 - the video

Happy glichin'! :p