Squirtle used to be the leader of a gang known as the Squirtle Squad, a group of rogue Squirtle who were deserted by their Pokémon Trainer. Meowth managed to befriend the Squirtle Squad by convincing them that Jessie and James were his pets. The Squirtle Squad then captured Ash, Misty and Brock so they could take Pikachu back to Meowth. Ash managed to convince the Squirtle Squad to let him free to get a Super Potion for Pikachu, who was badly injured after an earlier encounter with a Goldeen. The Squirtle Squad agreed to let Ash go to town to buy a Super Potion, but if he didn't return by noon the next day, they threatened to dye Misty's hair purple (in the original, they threatened to kill her).
During its time with Ash, Squirtle became one of Ash's three most trustworthy Pokémon, next to Bulbasaur and Pikachu, and it was used very often. It was first used in battle to repel Team Rocket Grunts aboard the St. Anne, joining a group of other Squirtle to use Water Gun on the Grunts. Squirtle's Water-type and ability to swim helped Ash in a few choice circumstances, notably the escape from St. Anne in Pokémon Shipwreck. In Tentacool & Tentacruel, Zubat carried Squirtle into battle with the giant Tentacruel, but they were easily swatted aside by a giant tentacle. In Pokémon Scent-sation!, it helped Misty's Water Pokémon fight the fire at Celadon Gym.When Ash got back with the Super Potion, Team Rocket began bombing the Squirtle Squad after they received Pikachu. Ash, Misty and Brock ran to hide in the Squirtle Squad's cave; however, when Ash noticed that the leader was stuck on his shell, he went back to save it, shielding Squirtle's body with his own. Dazed and with more bombs en route, Ash told Squirtle to save itself. So touched by Ash's loyalty, Squirtle burst into tears, summoned enormous strength, and carried Ash to the safety of the cave. Squirtle then defeated Team Rocket with Water Gun. However, Team Rocket's bombs had started a forest fire, which the Squirtle Squad worked together to put out. After putting out the fire, Officer Jenny appointed the Squirtle Squad as the official fire fighters of the town. The leader of the Squirtle Squad preferred to join Ash on his journey rather than fight fires alongside his group, as it wanted to repay Ash for saving its life during the bombing.
A Squirtle was featured in the XY series belonging to Tierno and it knows powerful moves such as Aqua Tail.