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

Amnesia Psyduck:
Get all 151 Pokemon in the hall of fame.

Start with all three beginning Pokemon in Game Boy game:
When you start a new game, you can start with all three beginning Pokemon by starting over and choosing one of them in the Game Boy Pokemon game. Then, capture a Pidgey or Rattata. Save it to the boxes on Pokemon Stadium. Repeat the steps with a different Pokemon until you get all three. You can also save and keep Pokemon from your old game that you still want before starting over.

Round 2:
Successfully complete the game to unlock a much harder version of the Stadium, Gym Leader's Castle, and Mewtwo Battle modes. If you defeat Mewtwo, you can use him in some battles.

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

Mewtwo Battle:
Complete all Cups in stadium mode, and defeat all opponents in the Gym Leader's Castle. Mewtwo is the last opponent you will face in both Round 1 and Round 2 versions of the game.

Defeating Mewtwo easily with rental Pokemon:
Select Electrode , and five other Pokemon that know one-hit K.O. attacks (i.e. Horndrill, Fissure, Guilliotine). Send out electrode first and use Thunder Wave -- this will allow all of your Pokemon to get the first attack. Do not attack mewtwo with Electrode - you do not want him to use Rest, which will get rid of the paralyzation. Send out another Pokemon and use the one hit K.O. attack. If that Pokemon faints, send out the next one and try again. This will defeat Mewtwo in one hit.

Bonus Stickers:
Successfully complete R-1 mode, defeat Mewtwo, and complete R-2 Mode, and defeat Mewtwo again. Enter the gallery screen, then hold L + R and highlight the "Print" option. Keep holding the buttons until "Print" changes to "Bonus" to access sixteen more stickers.

Change background:
After unlocking Doduo and/or Dodrio mode, when in Game Boy tower, play your game then press Z.

Inflict greater damage:
While your Pokemon is doing the attack, hold Down + L and repeatedly press A. Then when your Pokemon 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.

Easy wins:
Get Articuno, Zapdos, and Moltres, and three other Pokemon of your choice. Start with Zapdos against Lorelei. This should be a quick win. For Bruno, use any of the three legendary Pokemon. Against Agatha, use Articuno's Ice Beam for decent win. Against Lance, use Zapdos. He almost always uses Lapras. Use Zapdos' Thunder attack. When he uses the others, switch to Articuno or keep Zapdos. Finally against your rival, use Zapdos. He will most likely use Slowbro, the Clefable, and the last one usually changes. After you defeat him, it should show which Pokemon were on your team. At this rate you will only get three Pokemon at a time in the Hall of Fame.

Pokemon weaknesses
Normal Pokemon are weak against Fighting types.
Fire Pokemon are weak against Water, Ground and Rock types.
Water Pokemon are weak against Electric and Grass types.
Electric Pokemon are weak against Ground types.
Grass Pokemon are weak against: Fire, Ice, Poison, Flying and Bug types.
Ice Pokemon are weak against Fire, Fighting and Rock types.
Fighting Pokemon are weak against Flying and Psychic types.
Poison Pokemon are weak against Ground, Psychic and Bug types.
Ground Pokemon are weak against Water, Grass and Ice types.
Flying Pokemon are weak against Electric, Ice and Rock types.
Psychic Pokemon are weak against Bug types.
Bug Pokemon are weak against Fire, Poison, Flying and Rock types.
Rock Pokemon are weak against Water, Grass, Fighting and Ground types.
Ghost Pokemon are weak against Ghost types.
Dragon Pokemon are weak against Ice and Dragon types.

Alternate Pokemon colors
Pokemon that you upload from the Game Boy version can have alternate colors. Giving your Pokemon various nicknames will change its colors. Switch syllables, such as calling a Mewtwo to "Twomew" (blue color). Separate the syllables with a hyphen, such as Mewtwo to "Mew-two". Also try naming the Pokemon in all lower-case characters. To find out more methods, note the color of the opposing Pokemon and look at their nicknames.

Naming a Pokemon after an attack will change its color. Note: This does not work for some attacks, and some Pokemon either will not change color or will do so very slightly. This is not limited to attacks that the Pokemon know or can learn. Some examples:

"HYDRO PUMP": Dark Blue Gyarados
"PSYCHIC": Red Mewtwo
"METRONOME": Neon Yellow Pikachu
"THUNDER": Dark Orange Jolteon and Pikachu
"PIKACHAIN" or "PIKACHUPICACHAN": Green Pickachu
"SLEEPY": Light Green Snorlax
"PUNCHMAN": Green Hitmonchan
"BULBACE": Yellow eyed and tongued Bulbasaur
"BASSFAIRY": Light peach color, green eared Clefairy
"FIRE-BLAST": Neon yellow, orange flamed Magmar
"CASPER" Turquoise blue Haunter
"THUNDA": Lime green Zapdos
"RAZOR-LEAF": Royal blue, Orange petaled Venusaur
"WRAP": Yellow Bellsprout
"CARNIVORAS": Turquoise blue Bellsprout
"DRAGONZORD" Dark red charmander
"ACID" Luminious green-blue, Purple eyes Tentacool
"MAN-TIS" Orange eyes, Purple body, Blue feet Butterfree
"FINGKOF" Blue, Purple Koffing
"KOFSTOR" Red, Green sign Koffing
"LYGAST" Gastly with a Gold tongue
"MAGIMER" Orange or a Dark Red Magikarp
"HYDRO PUMP" Dark Blue Lapras
"CLAM" Blue Shellder
"SUPERSONIC" or "HAZE" Luminous green body, Purple winged Zubat
"DIG" or "ROCK SLIDE" Turquiose blue Geodude
"SOLAR WAVE" Red eyes, Purple body, Blue feet Butterfree
"PSYDANCE" Dark Yellow Psyduck with Black hair
"VICTRACE" Victreebel with yellow leaves and an orange-brown body with yellow spots.
"ELECTRACE" Electrode with a violet-red bottom half.
"VINCENT" Violet Hanter.

Special moves
Seismic Toss and Night Shade are special moves. The damage they inflict is equal to their level. A level 63 Gengar will inflict 63 HP damage to the other Pokemon, regardless of type, level, or defense. A level 76 Machamp will inflict 76 HP damage to the other Pokemon, regardless of type, level, or defense (except for ghosts, which are immune to normal moves). Also, Psywave inflicts HP damage 1 to 1 1/2 times the level of the attacking Pokemon. A level 50 Alakazam can inflict anywhere from 50-75 HP damage regardless of Pokemon type, level, or defense.

Flying Poke Cup roof lights
Win the Vs. Mewtwo battle to see the credits. When a scene showing the Poke Cup Arena appears, look at the roof lights to see that they are flying.

Ineffective moves
When battling normal type Pokemon do not use Seismic Toss. It can be a fighting move, but is not very effective. The same happens with the Mega Drain attack when battling some Ground Pokemon in the Poke Cup, Prime Cup and Gym Leader's Castle.