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.
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.
Battle Mewtwo
To unlock a hidden 6-on-1 battle with Mewtwo, beat the Gym Leader Castle and get trophies in all 10 tournaments in the Stadium Mode. The map screen will now turn to a night scene and a bonus tournament will open up in which you battle against the psychic super-Pokemon, Mewtwo (#150). Once you beat Mewtwo, you unlock a new game mode.
Faster Game Speed
Beat the game on prime cup (master ball) and go to gb (game boy) tower and press C-Right or C-Left and a sticker will be there amd the game will go faster.
Game Shark codes without a Nintendo 64 Game Shark
The "Import" feature and import pack can be used with Game Boy Game Shark codes while playing the original game or codes designed for it.
GB Speed Upgrades
There are two secret speed upgrades to the GB Tower Game Boy emulator that let you play Pokemon Red, Blue and Yellow at much higher speeds:
Doduo Mode: Beat the Poké Cup. Once you have won all the Poké Cup tournaments, the GB Tower changes into Doduo GB Tower and a Doduo sticker appears on the Game Boy. The Doduo upgrade doubles the speed of the game play when playing the Game Boy game on your N64.
Dodrio Mode: Play the Game Boy games at hyper speed with this alternate speed settings. To get it, you need to beat the Prime Cup (after you have already beaten the Poké Cup). You can switch between the different GB Tower speed settings during gameplay by pressing C Right.
Get Togepi
Get a Bulbasuar, and fight and win against Venusaur, Mewtwo, and Blastoise. After you have beaten them, go to Pokemon Lab and use the new item called Toge-Stone. Use it on Bulbasuar and you will have Togepi.
Missingno warning
Do not transfer Missingno to Pokemon Stadium. It will glitch the game and make it unplayable.
More Damage
When executing a fighting move, hold A when the description of the move is displayed.
New Title Screen
Beat both the Gym Leader Castle and Stadium modes to change the title screen (in addition to the map mode). The new title shows depict Pikachu, Blastoise, Charizard, Venusaur and Mewtwo.
Open Up R-2 Mode
To get the secret R-2 Mode (as well as a brand-new title screen) defeat Mewtwo after you have beaten the Stadium Mode and Gym Leader Castle Mode. You will now see the final credits sequence, which will unlock the harder R-2 Mode and all new battles. You can toggle between R-2 and Regular Mode at the start-up screen.
Pikachu talks
If you import a Pikachu from Pokemon Yellow, he will actually talk when he is battling.
Play Pokemon faster
Successfully complete the entire Poké Cup to get a sticker on the GB Tower. This will allow you play Pokémon on the Nintendo 64 twice as fast. If you beat the Masterball in the Prime Cup, a "Superfast" setting will be unlocked in the GB Tower. The title will change to "Doduo GB Tower". Press C-Left to activate it.
Pokémon weaknesses
Normal Pokémon are weak against Fighting types.
Fire Pokémon are weak against Water, Ground and Rock types.
Water Pokémon are weak against Electric and Grass types.
Electric Pokémon are weak against Ground types.
Grass Pokémon are weak against: Fire, Ice, Poison, Flying and Bug types.
Ice Pokémon are weak against Fire, Fighting and Rock types.
Fighting Pokémon are weak against Flying and Psychic types.
Poison Pokémon are weak against Ground, Psychic and Bug types.
Ground Pokémon are weak against Water, Grass and Ice types.
Flying Pokémon are weak against Electric, Ice and Rock types.
Psychic Pokémon are weak against Bug types.
Bug Pokémon are weak against Fire, Poison, Flying and Rock types.
Rock Pokémon are weak against Water, Grass, Fighting and Ground types.
Ghost Pokémon are weak against Ghost types.
Dragon Pokémon are weak against Ice and Dragon types.
Recommended Round 1 rental teams
Pika Cup
Raichu, Poliwrath, Arcanine, Exeggutor, Drowzee, Dratini.
Petit Cup
Pikachu, Bulbasaur, Horsea, Sandshrew, Gastly, Dratini.
Poké Cup, Poké Ball
Diglett, Abra, Staryu, Jynx, Magmar, Jolteon.
Great Ball
Dugtrio, Persian, Abra, Staryu, Jynx, Jolteon.
Ultra Ball
Fearow, Dugtrio, Kadabra, Dewgong, Starmie, Jolteon.
Master Ball
Sandslash, Kadabra, Gengar, Starmie, Electrode, Articuno.
Prime Cup Poke Ball
Pikachu, Voltorb, Diglett, Abra, Poliwhirl, Weepinbell.
Great Ball
Electabuzz, Pikachu, Kadabra, Magmar, Dewgong, Dugtrio.
Ultra Ball
Charizard, Dugtrio, Kadabra, Dewgong, Electrode, Gengar.
Master Ball
Dugtrio, Arcanine, Kadabra, Dewgong, Electrode, Exeggutor.
Pewter Gym
Charmander, Wartortle, Growlithe, Abra, Weepinbell, Voltorb.
Cerulean Gym
Kadabra, Weepinbell, Voltorb, Staryu, Hitmonlee, Vaporeon.
Vermilion Gym
Sandshrew, Dugtrio, Gengar, Electrode, Cubone, Dragonite.
Celadon Gym
Kadabra, Electabuzz, Dewgong, Flareon, Hitmonlee, Mr. Mime.
Fuchsia Gym
Dugtrio, Kadabra, Cloyster, Gengar, Electrode, Mr. Mime.
Saffron Gym
Dugtrio, Kadabra, Electrode, Omanyte, Flareon, Dragonite.
Cinnabar Gym
Gengar, Electrode, Kingler, Mr. Mime, Vaporeon, Snorlax.
Viridian Gym
Kangaskhan, Gengar, Electrode, Dragonair, Alakazam, Starmie.
Elite Four and Rival
Gengar, Dragonair, Staryu, Jolteon, Scyther, Electrode.
Mewtwo
Electrode, Ditto, Fearow, Cloyster, Mr. Mime, Magneton.
Recommended Round 2 rental teams
Pika Cup
Raichu, Lapras, Ninetales, Gengar, Nidoking, Kadabra.
Petit Cup
Voltorb, Spearow, Horsea, Abra, Cubone, Gastly.
Poké Cup, Poké Ball
Dugtrio, Alakazam, Starmie, Tauros, Lapras, Jolteon.
Great Ball
Dugtrio, Alakazam, Exeggutor, Starmie, Tauros, Jolteon.
Ultra Ball
Dugtrio, Alakazam, Gengar, Starmie, Jolteon, Articuno.
Master Ball
Dugtrio, Alakazam, Exeggutor, Starmie, Lapras, Jolteon.
Prime Cup Poke Ball
Poliwhirl, Electrode, Weepinbell, Drowzee, Machoke, Marowak.
Great Ball
Fearow, Gengar, Golduck, Magneton, Hypno, Dugtrio.
Ultra Ball
Exeggutor, Electrode, Lapras, Rhydon, Mew, Dragonite.
Master Ball
Electrode, Exeggutor, Starmie, Golem, Mew, Jynx.
Pewter Gym
Electabuzz, Doduo, Magmar, Krabby, Paras, Diglett.
Cerulean Gym
Magnemite, Seadra, Gastly, Staryu, Aerodactyl, Tangela.
Vermilion Gym
Parasect, Magneton, Fearow, Haunter, Pinsir, Dragonair.
Celadon Gym
Pidgeot, Ninetales, Raichu, Poliwhirl, Dragonair, Tangela.
Fuchsia Gym
Alakazam, Electabuzz, Dugtrio, Gengar, Dodrio, Poliwrath.
Saffron Gym
Gyarados, Gengar, Jolteon, Mr. Mime, Exeggutor, Dugtrio.
Cinnabar Gym
Starmie, Fearow, Exeggutor, Gengar, Alakazam, Electrode.
Viridian Gym
Electrode, Zapdos, Jynx, Exeggutor, Gyarados, Dugtrio.
Elite Four and Rival
Starmie, Lapras, Dragonite, Electrode, Exeggutor, Gengar.
Mewtwo
Electrode, Snorlax, Zapdos, Alakazam, Golem, Gengar.
The Stadium Cups:Hint
Raise your own pokemon on Red, Yellow, or Blue version so you will have better stats and you can custom your moves for the stadium cups.
Trade with out a second transfer pak
Put a box on the game, then put the Pokemon 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 Pokemon when you want or need it. Note: This also works with items.