There are a number of common, uncommon, and rare Pokemon out in the wilds of Kanto. However, there’s a small number of Pokemon that are so rare that you can only find one of each during a single playthrough of the game. These are not the mythical or Legendary Pokemon with long tales surrounding their history. They’re actually given away as gifts!
Bulbasaur, originally a choice for a starter Pokemon in Red and Blue, can be obtained completely for free in Cerulean City. Speak to the woman in the house west of the Pokemon Center. If your Pikachu likes you enough, she’ll give you the grass dinosaur.
Charmander, originally a choice for a starter Pokemon in Red and Blue, can be obtained completely for free at the northwest portion of Routes 24 and 25, just north of Cerulean City. Speak with the Pokemon Trainer standing alone to add the fire lizard to your team!
Squirtle, originally a choice for a starter Pokemon in Red and Blue, can be obtained completely for free in Vermilion City. After defeating Lt Surge and obtaining the Surge Badge, speak with Officer Jenny near the Poke Mart to add the water turtle to your team!
Hitmonlee and Hitmonchan
Hitmonlee and Hitmonchan are one set of rare Pokemon in Red, Blue, and Yellow. After defeating the leader at the Fighting Dojo in Saffron City, he will allow you to choose between the two. Hitmonlee has better attack and speed, but Hitmonchan has better defense and elemental punching attacks.
Mr. Mime is another Pokemon that can be obtained from an in-game trade. You can find the person offering the Mr. Mime in a house on the east side of Route 2. He’ll ask for a Clefairy in Pokemon Yellow.
Lapras will be given to you completely for free by a worker within Silph Co. in Saffron City. This person is in the same room as the Rival battle.
A Poke Ball containing an Eevee will be left out on a table at the top of the Celadon City Apartments. You’ll need to enter from the back door to reach the room with the Poke Ball.
Porygon is an incredibly rare and unusual Pokemon. It’s probably the hardest rare Pokemon to get in the game because you have to get it on luck. It can be purchased at the Celadon City Game Corner for 9999 coins in Pokemon Yellow, which means you’ll have to gamble at the slot machines to earn the coin. You can purchase 50 coins with P1000, but even if you buy 9950 coins with P199,000, you’ll have to gamble for the remaining 45.
Omanyte and Kabuto are another set of rare Pokemon that you must choose from. While in Mt. Moon you’ll come across two fossils just before the exit. You will only be able to choose one, so choose wisely. Take this fossil to the Pokemon Lab on Cinnabar Island to revive it into one of these Pokemon. The Helix Fossil become Omanyte, and the Dome Fossil becomes Kabuto. Both can then evolve once they reach the appropriate level. Kabutops (the evolved form) specializes in attack while Omastar specializes in special.
Aerodactyl is another rare Pokemon that can be revived from a fossil. The fossil you need is called Old Amber, and it can be found at the Museum in Pewter City. You’ll need a Pokemon that knows Cut to chop down a bush on the east side of the Museum first. Take the Old Amber to the Pokemon Lab on Cinnabar Island to revive it.
Snorlax is another rare Pokemon, but there are actually two in the game. If you don’t capture either one, you won’t have another chance. One is blocking the path to the west of Celadon City, and the other is blocking the path to the east of Route 11 and Vermilion City. Use a Poke Flute to wake them up and begin battle. The Poke Flute can be obtained from Mr. Fuji after rescuing him at the top of Pokemon Tower in Lavender Town.