Missingno.

To catch Missingno first go to the guy in Viridian that catches a weedle and when he asks you if you're in a hurry say "No".

Then he catches his weedle and after that fly to Cinnabar and Surf on the east side after a few minutes you will find Missingo. WARNING If you catch him he will mess up your graphics and the only way to solve it is to erase the game.

Infinite Money

Do the same as the Missingno. code but put a nugget in the sixth spot in your item list before fighting him. When you beat him look at your items and the nuggets are multiplied.

Fake codes

None of these codes work so if you see it on another site ignore them!

Ultra Rod

Talk to the guy who gives you a Super Rod 100 times and you'll get the Ultra Rod which allows you to fish for Hm's as 6 and 7.

6 is Hi-Fly and 7 is Deep Dive.

If you want a Mew, go to the Poke center up by mount moon and buy a Magikarp from the guy there. You know that it is at Level 5 so put it in the daycare until he says that he's grown by 45. When he gets there take him out and level him by one.

Finally, he will start blinking and evolve into Mew.