How to Get a Squirtle in "Pokemon: Pearl"by Tucker Cummings ; Updated September 22, 2017
Squirtle, a cute, blue, turtle-like creature, was a classic part of the game for fans of the first generation of "Pokemon" titles, "Pokemon: Red Version" and "Pokemon: Blue Version." However, when "Pokemon: Pearl Version" was released, the game no longer included Squirtle. While players cannot capture Squirtle in the "Pearl" version of "Pokemon," that doesn't mean that it's impossible to use a Squirtle in the game at all. Players have two main ways to get a Squirtle to use in-game for "Pokemon: Pearl Version."
Travel to Sandgem Town and speak to Professor Rowan at Lake Verity. He will drop some items that you must return to him.
Return the items to the Professor at his lab. Once you have done so, he will give you an upgraded Pokedex.
Connect your game and game system with a friend who has a compatible version of "Pokemon" (either "LeafGreen" or "FireRed"). Your friend can then give you a Squirtle.
Locate the Pal Park closest to your current location. One is located in Fuschia City, and the other is on Route 221 in Sinnoh.
Before entering the park, make sure you have transferred at least six Pokemon from one of the following versions of the game: "Ruby," "Sapphire," "Emerald," "FireRed," "LeafGreen." The Pokemon you transfer must be of the same language/country of origin as your own copy of "Pearl."
Speak with Professor Oak or the Warden's Son -- who you speak to depends on which park you are at. Follow the character's instructions, and select the "Migrate" option.
Trading is only supported on the Nintendo DS for "Pearl."
Migrating a Squirtle into "Pearl" cannot be reversed.