Surfing Pikachu
Successfully complete the game to unlock Surf for Pikachu. To teach your Pikachu Surf, unlock Round 2. Then, get up to the Masterball setting on either the Poké Cup or Prime Cup (in Round 2). Complete the Masterball setting with Pikachu as one of your active Pokémon each round (he must be one of the three you choose to battle with). If you lose, you cannot continue (it must be a pure win and the Pikachu may not be part of a registered team or a "Rental"). If you succeed, the game will congratulate you and ask if you would like to replace one of Pikachu's moves with Surf. Select "Yes", then choose the move to be forgotten. The Pikachu will now pull out a surfboard and ride the wave whenever Surf is used.You can also get a surfing Raichu! Get a Raichu that knows SURF (as seen by Surge's Raichu). It will put its tail under itself and use it as a surfboard.

Talking Pikachu
Upload Pikachu from the yellow version of the game to Pokémon Stadium. When battling, Pikachu will say its name and have different motions for certain moves. Note: You must go to battle for this to work. Do not register Pikachu.

Mew
Mew will become playable, as a "Rental" Pokémon, in the Round 2 version of the game. He can only be played in the Prime Cup tournament, Gym Leader Castle, Free Battle, and Mewtwo Battle modes.

Mew in Prime Cup
This trick requires a Game Boy Game Shark and Pokémon Yellow. First start the game and enable the Game Shark code to catch Mew. Put it first in your line-up, then save the game. Go to the Game Shark screen and enable the code for the first Pokémon in your line-up to be any desired Pokémon. Check your stats and it should display your selected Pokémon's picture, but with Mew's name and information. Save the game. Place the game in the transfer pak and go to the Pokémon Stadium building. When prompted to select Pokémon, choose the one that was Mew. When you start the match, the Pokémon will be Mew.

Mewtwo Battle
Beat Gym Leader Castle and all Stadium Cups in order to go against Mewtwo.You will end each round battling him.

Round 2
Successfully complete the game to unlock a much harder version of the Stadium, Gym Leader Castle, and Mewtwo Battle modes.

Kids Club Hyper mode
In one player mode with three CPU controlled opponents, successfully complete "Who's the best?" five consecutive times on the hard difficulty setting within one match. Hyper will be unlocked as a new difficulty setting for CPU controlled players.

Get Pokémon presents faster
Successfully complete the Gym Leader Castle. Then when you want to complete it again, go to the Gym Leader Castle, go directly to the Elite 4, and defeat your rival.

Avoid recoil damage
If you use an attack that you know will kill the opposing Pokémon, but will hit you with the recoil, make sure that your Pokémon has at least 20 HP left. Use the attack and you will not suffer the recoil damage.

Take less damage
Use the following trick when your Pokémon is receiving a fatal attack, such as when Thunder is used on a Water Pokémon, to leave you with enough HP to attack your opponent once. When your opponent's Pokémon begins to use their attack, hold Down + L + B until the energy takes its affect. When the energy leaves, you will have a chance to strike your opponent's Pokémon. Note: This trick only works between 70% to 80% of the time. This will not work if Pokémon are totally mismatched, such as when a level 50 Pokémon is fighting a level 100 Pokémon.

Inflict greater damage
While your Pokémon is doing their attack, hold Down + L and repeatedly press A. Then when your Pokémon attacks, hold Down + L + A until the damage is taken. This is very effective when you attempt a fatal attack. Note: This trick only works between 80% to 90% of the time.

Attack first
Immediately after you choose a move and you want to go first instead of the CPU, hold L and press A. Note: This trick only works about 50% of the time, mostly in the Pika Cup.

Trade without a second transfer pak
Put a box on the game, then put the Pokémon from a different game or the same one in the box. Then, go back to the lab and put the box back on the game that you are trading to, go to the box, and withdraw the Pokémon when you want or need it. Note: This also works with items. Give Pokémon to another Game Boy pak without getting one back Place the desired Pokémon in a separate box from which you have your regular Pokémon. Transfer that box to the 64box on the Nintendo 64. Shut off the system (if you only have one transfer pak) and insert desired Game Boy pak. If you have two transfer paks, then just switch the Game Boy pak with the one you are going to trade to. Then, transfer the box with the Pokémon in it to the other Game Boy pak and you will have the Pokémon without giving one in return.