Squirtle used to be the leader of a gang known as the Squirtle Squad, a group of rogue Squirtle who were deserted by their Trainers. 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).
Squirtle saving Ash, after Ash had done the same
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 his life during the bombing. After being accepted, it happily ran into Ash's arms, as the trainer declared he had caught a Squirtle.
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.
Squirtle bearing Pikachu across the water
It served as Pikachu's 'steed' when the group competed in a race in Ash's place (Ash having taken Lara Laramie's place on Ponyta). The two were at a significant disadvantage due to Squirtle's short legs and Pikachu's comparative weight, but in a way this helped as they managed to escape the Electrode self-destructing. They made ground when they reached the water stage, putting them in the top four with Ash, Misty and Dario. However, intervention from Team Rocket forced a battle, and the two were put out of the running by a Glare attack from Arbok.
In Attack of the Prehistoric Pokémon, Squirtle desperately tried to stop a fuse from detonating explosives, but failed and this resulted in Pikachu, Ash and Team Rocket being trapped underground with hostile Prehistoric Pokémon. Only Squirtle was rescued from the rubble by Misty and Brock. It then did its best to rescue its Trainer. In The Battling Eevee Brothers, it was used by Ash when Team Rocket was trying to evolve Eevee. However, it and the attack it planned to use were interrupted when Psyduck got in front of it and tried to use a Water Gun of its own before failing. Despite this minor delay, Squirtle was still able to use Water Gun on Team Rocket, sending the group backwards. In The March of the Exeggutor Squad, it was used in an attempt to con Melvin into believing Ash was able to magically control water and fire with the use of a box, that inside contained Squirtle, Bulbasaur and Charmander. After being burned by Charmander, the three started to fight and thus, ruined the trick that Ash was pulling at the time. Though accidental, Melvin managed to gain control of Ash and snuck away with him to the Leaf Forest. Ash was commanded by Melvin to weaken the Exeggutor with his Pokemon, causing Ash to send out Squirtle, Bulbasaur and Charmander. It was used to weaken the Exeggutor as Melvin intended, shooting one in the legs with its Water Gun. After aiding Melvin and the mind-controlled Ash, it became tired and rested with Charmander and Bulbasaur as Melvin expressed enjoyment in having captured the Exeggutor and Team Rocket arrived to steal his Pokemon. Squirtle would participate in defeating the Exeggutor after they proved too much for Melvin to handle.
In The Song of Jigglypuff, it was put to sleep along with the rest of the group's Pokemon by Jigglypuff. In Attack of the Prehistoric Pokémon, it was sent out by Ash to stop a fire set by Team Rocket after they let Meowth light a fuse. Squirtle joined Ash and Pikachu in chasing after the fuse, being chased by Team Rocket and their own Pokemon while doing so. He collides with Team Rocket, their Pokemon and Pikachu before they all fell into Ash. After the dynamite detonated, Squirtle would be the only one to escape from the rumble. He tried to aid Ash and Pikachu in getting out by digging through rocks with Brock and Misty before being joined by Geodude. It would witness their escape and Charmeleon's evolution into Charizard. Squirtle was used to weaken a Dodrio in A Chansey Operation, where Ash ordered it to use Water Gun before being followed by Pikachu with his use of Thunderbolt. Though Ash planned to capture the Dodrio after their work, Brock reminded him that they wanted to merely helped the Pokemon. In The Purr-fect Hero, Squirtle was sent out by Ash to play with a few children along with the rest of the group's Pokemon, giving one little boy a ride on its shell.
It was used again in Pokémon Paparazzi, where it used Water Gun after being ordered by Ash to shot a photographer by the name of Todd Snap before the two became acquainted. Once they were, Squirtle was sent out again along with the rest of the group's Pokemon to be photographed. In Beach Blank-Out Blastoise, Squirtle was instrumental in helping rescue a colony of Squirtle, Wartortle and a Blastoise from Jigglypuff.
Squirtle's Gym Battle debut came late and its Kanto Gym record was two losses, the first to Blaine's Ninetales in Riddle Me This, who Ash believed would be disadvantaged against Squirtle. Ninetales' Fire Spin completely overpowered Water Gun and took Squirtle down in one hit. It was then sent out to fight the fire in Volcanic Panic to cool off Geodude, Onix and Pikachu with water as they dammed the volcano. The second loss was against Giovanni's Machamp, under control of Jessie in The Battle of the Badge. Squirtle took damage from Machamp's Karate Chop, leading to electric shocks blasting Ash. The battle was ended when Giovanni's Pokémon defected and Team Rocket was sent blasting off.
In Mewtwo Strikes Back, Squirtle was used to battle Raymond's Machamp and defeated it with Bubble Beam. On New Island, Bulbasaur and Squirtle attempted to resist capture by Mewtwo, using its Water Gun to keep the Balls at bay. Ash recalled both Pokémon to safety, but both were cloned when Squirtle's Ball was captured itself. Squirtle fought viciously against its clone, but found itself overwhelmed. It wept when Ash was petrified by Mewtwo and Mew, its tears helping in his restoration, along with the clone created from it and the other original and clone Pokemon.
Squirtle landing the knockout blow in the second round of the Indigo League, with its signature finisher, Skull Bash
In All Fired Up!, it bravely leapt to Ash's aid against Team Rocket by jumping on Jessie's face in an attempt to rescue the Great Torch, having already saved Team Rocket from fire. Ash relied on Squirtle to battle Mandi in Round One - Begin!, but his powerful Kingler took the sweep and Squirtle was unnecessary. However, it won Ash's second round by defeating a Nidorino, revealing its ability to use Withdraw to absorb the Nidorino's Tackle, and then rolled across the rocky battlefield. It rolled up a rock pillar to become airborne and hit Nidorino with Water Gun. This was followed up with Skull Bash and won the battle for Ash.
In Friend and Foe Alike, Squirtle was sent out to battle Ritchie's Butterfree, Happy. However, it was easily put to sleep by Sleep Powder and Ash lost the round. Despite his loss, Ash was honored at Pallet Town along with Gary in Pallet Party Panic for representing the town in the Indigo League and found himself in attendance, sending out Squirtle and the other Pokemon out to enjoy the food made for them. Team Rocket jinxed the food by implanting spices to make it ridiculously hot, something Squirtle noticed after having taken a bite of the food. The heat of the meal was so overbearing that it was unable to use Water Gun, instead having to be cooled down by Staryu. After defeating Team Rocket, Ash decided to go to the Orange Islands, to deliver the GS ball to Professor Ivy. Squirtle accompanied him, being used in A Scare In The Air to aid the group in getting off of the plane Team Rocket tricked them on and having a bumpy ride while landing.
Squirtle was used more prominently in the Orange Island Gyms, first in competition against Cissy's Seadra in Fit to be Tide. Both Pokémon had to shoot cans with Water Gun, but when they hit the final can at the same time, the match resulted in a draw. Though it did not win, Ash still congratulated it on its admirable work.
In Naval Maneuvers, it joined Bulbasaur, Pikachu and Ash in steering the ice sled down the mountain, resulting in a win for Ash. It was also sent out to battle a wild Snorlax in the next episode, but was flattened by Body Slam, having done completely nothing. In The Mandarin Island Mis-Match, it defeated a Trainer's Persian with Skull Bash, but was defeated by a single Take Down from the Trainer's Tauros.
Learning Hydro Pump to overcome Rudy's Starmie
One of Squirtle's most notable battles and its only Gym Battle win was in Misty Meets Her Match. Earlier in the episode, it helped Pikachu and Bulbasaur destroy the targets, before coming out third against Rudy's Starmie. Its powerful Water Gun managed to match Squirtle's, and Rudy's music allowed Starmie to dance away from Squirtle's moves and then use Thunderbolt to knock Squirtle into submission. With encouragement from Misty, Squirtle propelled itself away from Thunderbolt and while using Withdraw, learned Hydro Pump to become airborne and hit Starmie hard. Closing the battle with Skull Bash, Ash wins the battle and his third Orange Island Gym Badge.
In The Pokémon Water War!, Squirtle attempted to rescue a warehouse on fire, but when the fire spread, it needed rescuing itself by Captain Aidan and Team Wartortle. This shot Squirtle's confidence as a firefighter and Ash pleaded with Aidan to allow Squirtle to train with his team for a short period. However, they fell into a Team Rocket trap and were captured, but Squirtle's thinking allowed the group to escape: they flooded the cabin to allow mobility, and then trick Meowth into cutting the nets, before blasting Team Rocket away. Squirtle then joins the effort at a burning apartment and halts the fire, saving the day.
In Hello, Pummelo!, Squirtle was sent against Drake's Onix, who managed to evade Water Gun with Dig, and then caught Squirtle with Bind. However, Squirtle broke free with a Withdraw/Hydro Pump combination, then hit Onix with Skull Bash to knock it out. In the next episode, it fought Dragonite, only for its Hydro Pump to be countered by Dragonite's Water Gun. Squirtle was able to use Withdraw in time to evade most of the following Thunderbolt, but was still badly hurt. Squirtle used Bubble Beam to hit Dragonite dead-on, but this was the only successful attack and it was beaten by a slam from Dragonite's tail. Pikachu went on to defeat the exhausted Dragonite and Squirtle earned a place in the Orange Islands Hall of Fame.
Squirtle accompanied Ash to Johto as well, the final time it would serve as a permanent member of his team. In Don't Touch That 'dile, Squirtle was used against Team Rocket with Bulbasaur, Pikachu and Charizard. Combining its Water Gun with their attacks, it fired directly on Team Rocket's Pokemon. In The Double Trouble Header, it was sent out to battle against Team Rocket along with Bulbasaur after they captured Pikachu and Chikorita. During its time with him, it and Bulbasaur showed concern for him on occasions, such as when Ash, Pikachu and his soon to be caught Chikorita were lost in a snowstorm in The Chikorita Rescue. In Once in a Blue Moon, a Quagsire stole the GS Ball and swam away. Ash tried to run after it, but ended up sending out Squirtle to chase it down. After failing to wrestle it out of the Quagsire's mouth, Squirtle used Water Gun, causing the GS Ball it slips out of Quagsire's mouth, and allowing Pikachu to catch it on the shore. While both Quagsire and Squirtle were using Water Gun against each other, Misty tried once again to catch it, but before throwing the Poké Ball, Officer Jenny stopped them and arrested them for violating the Quagsire Preservation Restrictions. Squirtle would again be used in Ignorance is Blissey, where it was deployed with Chikorita to retrieve some food that Team Rocket had stolen. It used Water Gun on Jessie, James and Meowth while Ash's other Pokemon attacked their Pokemon.
In The Fire-ing Squad!, it competed in an event called the Fire and Rescue Grand Prix, a firefighting competition for water Pokémon. As luck would have it, one of the teams was the Squirtle Squad, but they were confused without their leader. Ash's Squirtle led the Squirtle Squad to win the Grand Prix, and at the end of the episode Squirtle returned to the Squirtle Squad because Ash felt that the old gang needed Squirtle more than he did. It said goodbye to its friends and Bulbasaur extended a vine to its long-time friend, shaking solemnly.
It returned briefly to battle in the Silver Conference, after Kingler was badly injured by a group of renegade Voltorb. It joined Totodile and Phanpy against the Fire-type trainer Macy. It was Ash's last Pokémon, faced with an advantaged Electabuzz. However, Squirtle proved much faster and managed to hit Electabuzz with a series of Water Guns before it could launch any Electric-type moves. A Skull Bash was enough to knock out Electabuzz and even up the match for Ash, leaving just Quilava left. Squirtle used an explosion of moves to cover a stealthy Water Gun, but was hit and knocked on its back by Quilava. As Macy went in for the knock out, Squirtle used Hydro Pump to hit Quilava with water and its own body, sealing victory for Ash.
In Tie One On!, Squirtle and Bulbasaur rekindle their friendship, but Squirtle starts a fight with Jackson's Azumarill and Meganium. Bulbasaur attempts to restrain its hotheaded companion, but ends up becoming angry at Meganium and Azumarill when they play dirty and trip it over. Squirtle stayed around to watch Ash's Silver Conference battles, and then left in Johto Photo Finish!
Advanced Generation series
While Squirtle made no appearances during the Hoenn arc of the Advanced Generation series, it did make an appearance, along with the rest of the Squirtle Squad, in Of Meowth and Pokémon (Part 2). Squirtle and two other members of the Squirtle Squad ambushed Smoochum and attacked her with a Water Gun, sending her flying.
Kanto Battle Frontier
Squirtle can be called upon at any time. In Gathering the Gang of Four!, it returned to help Ash with his final battle against Brandon, meeting May's Squirtle. It expressed happiness in seeing Bulbasaur and Pikachu again and departed with the two, Ash and Charizard for the woods. Though tension between the group started to erupt, they settled their differences and sat as Ash recalled his meetings with the four of them. After Pikachu was captured by Team Rocket, Squirtle participated in saving his teammate with the others. In Pace - The Final Frontier!, it took on Brandon's Ninjask. Squirtle's Rapid Spin deflected Aerial Ace, but Ninjask gained the upper hand by stalling Squirtle with Double Team and hitting with Aerial Ace while Squirtle blasted through the afterimages. Squirtle managed to escape Sandstorm with Hydro Pump, but is blinded by Sand Attack to the eyes, leaving it exposed to Ninjask's attacks. It listens for Ninjask, but Hydro Pump misses. However, the water clears Squirtle's eyes and it Skull Bashes Ninjask dead-on, knocking it out of the battle.
Solrock came out next, but Squirtle's moves were all dodged or blocked by Psychic moves. A missed Rapid Spin saw Squirtle crash into the wall, and it was flattened by Solar Beam, causing it to lose the match. After the battle was won, Squirtle returned to the Squirtle Squad, where it still remains.
Best Wishes series
Squirtle appeared in a flashback in The Fires of a Red-Hot Reunion!.