Clone a pokemon
1.Hook up with a game link cable to your friends game to trade.
2.If 1 person has a pokemon that you want do this.
3.The 1 that doesn't have the rare pokemon trade a rattata.
4.When the trade is almost done the person who originally had the strong or rare pokemon when the screen says waiting turn your gameboy off before it says "trade complete".
5.Then the person with their gameboy on waits till it says"trade complete" and then turns their gameboy off.
6.When you turn your gameboy is back on you should both have the rare or strong pokemon and the common pokemon should be gone.

Glitch City
Go into the Safari Zone and say YES that you want to catch Pokemon. Walk around for a little bit, and then try to leave Safari Zone. When he asks you if you are leaving early, say NO. It will make you walk back into the Safari Zone. Leave again, and once more say NO. When you go back into the Safari Zone, save your game and then shut it off. Turn it back on and go out of the Safari Zone. This is when the first glitch appears. Instead of asking you if you want to leave early, he asks you if you want to join the hunt. When he asks you this, make sure to say NO again. Walk out of the house and FLY to Cinnabar Island. SURF up and down the coast until there is the gong you usually hear in the Safari Zone, although it may take a while. The game then warps you back to the Safari Zone and the man asks if you had a good haul and so forth. Leave the building, and when you go outside you are in a strange "Glitch City." It is very easy to get trapped in here, and the different glitches make it hard to move around. Some things to try are fishing, SURFing, and trying to find new paths. Just remember, nothing is what it seems. If you want to get out of the city, you must FLY out and save. It really doesn't matter where you FLY to; instead of Cinnabar Island, try Cycling Road or any other city and see what the difference is when you enter the "Glitch City." Cinnabar Island was just posted here because it makes the most interesting glitches in my opinion. But be Warned, this code could delete your game data.

Catch Pokemon near Cinnabar
Enter a cave with rare Pokemon, the Safari Zone, or fight a trainer. Exit this and FLY to Cinnabar Island. Surf up and down the right coast of the island and you should eventually encounter different Pokemon from where you just were.

Raise Pokemon's Stats
Take one Pokemon out. After battling many Pokemon, heal your Pokemon at a Pokemon Center, then deposit it into the PC. Take it out again and its HP and stats will have risen. This code works because every time you fight a Pokemon, you get a percentage of that Pokemon's stats added into a "pool." It accumulates no matter what Pokemon you fight, so if you want higher HP, fight many Chanseys. If you want higher speed, fight Pikachus. When you place a Pokemon that has been accumulating this "stat experience" into the PC, the experience is applied and your Pokemon's stats have risen.

Colour Code
You must use a Game Boy Color system for this code to work. When the words Game Boy Color flash across the screen when you first turn on the system, press the following buttons to change the colors of your game.
B and Right - This will turn all of the light colors dark and all of the dark colors light.
B and Left - This combo makes the colors go black and white, as if you were using an old Game Boy or Game Boy Pocket.
A and Right - This makes all of the colors have a green tinge, as if it is spring in the game or you are playing Pokemon Green.
B and Down - This makes all of the colors a light brown as if it were autumn in the game. *When you set the colors to Autumn, if you enter Rock Tunnel all the characteristics of the cave that were previously hidden in the darkness will now be visible.*
B and Up - This turns all of the colors into a dusty brown, darker than the autumn brown.
Down - Gives everything pastel colors.
Right - Turns every color into Christmas colors, red and green.
Left - Changes all of the colors to blue.
Up - This gives everything a chocolately color.

Invisible PC
Go to the people hotel in Celadon City. Go all the way to the center of the right wall. Go one step up and press A. You will log onto a PC just as if there were one there.

Infinite HP
First, do the Missingno. code (See Missingno. code) and catch a Pokemon over level 100. Feed him HP ups until it can't take any more, but don't heal the excess damage at all! Use Rare Candies on him until it grows over level 255. It should be on level 0, but it will have a strange symbol in front of the number. If you go into battle and get hit you will receive heavy damage, but you will never faint. Don't try to use potions, because you will keep on healing forever. Also, don't heal at a Pokemon Center or it will go back to normal.

Battle Cheat
Try this code out with a friend, then use it in actual play if the chance ever comes up. Have your opponent use Substitute. Use Explosion or Self Destruct while it is in effect. You will not lose any HP, and your Pokemon will temporarily lose its graphic. In order to get your picture back, you must let your opponent hit you or you must switch your Pokemon. Unfortunately, you can't do the trick again until he uses Substitute again!

Skip Seafoam Islands
If you don't know how to get past the Seafoam Islands, FLY to Pallet Town. Surf in that body of water all the way down to Cinnabar Island. You will not fight the trainers you would in Seafoam, and you won't get Articuno, but you do save a lot of time, and you can always go back!

Cut Grass
Get a Pokemon that knows CUT and step in front of grass or walk into it. Use CUT and your Pokemon will hack away the grass leaving the bare ground.

Cool Ditto
Take a Ditto and go to the strip of grass near Nugget Bridge and the Unknown Dungeon. Fight a Pidgey and use Transform. You'll get Gust, Sand-Attack, and Quick Attack. Using the SELECT button, switch Gust with Sand-attack. Defeat the Pidgey. Transform will be erased and will be replaced with a nameless move that has the type "Cooltrainer." Now get a PP up and an item, such as Max Elixer, that restores PP. Use PP-Up on Ditto's new attack. The game will show a glitch that imply's the attack's PP went up. These won't be restored in a PokeCenter, so in order to use the attack you must use Max Elixer, Elixer, Ether, or Max Ether to restore the PP. Now it is possible to use Ditto's new attack. It hardly ever hits, but if it does it will show two flashes of light and then do damage.

Gentleman on Roof
Surf up and down the east coast of Cinnabar Island. Climb out of the water so that you are next to Gym's door. Now, if you walk to the right, you will see an old man standing on the room of the Gym.

Ride Cycling Road without a bicycle
Deposit your bicycle into a PC and head over to Cycling Road. Try to walk past the guard, but he will stop you. While he is talking to you, keep holding LEFT. When he finishes talking to you, your man should continue to walk onto Cycling Road. When you enter, you will be on a bicycle even though you do not have one taken out.

*Note*
ALL codes I put on my website I have tested on my own versions of pokemon.
All are legitimate codes.