When Tierno was beginning his journey, he chose Squirtle from Professor Sycamore as his starter. Squirtle is a great battler and uses dancing moves in its battle strategies in order to evade hits. It managed to evade a Conkeldurr's Superpower by dancing and defeat it using Skull Bash. When Trevor's Charmander appeared before the heroes, it accidentally burned Clemont's Chespin, so Squirtle used Water Gun to douse the fire. Later, Ash chose Tierno as his challenger and used Froakie to battle his Squirtle. Froakie used Water Pulse, but Squirtle evaded by using its rhythm strategy and defeated him with Rapid Spin.
The following day, Tierno took Squirtle to climb a part of a mountain with him to collect a stamp. Once they found Bonnie, who went missing during the race, Tierno had Squirtle attack some Drifloon and Drifblim with Water Gun, causing them to float and allow Ash to jump onto them to save Bonnie. However, when Ash was returning, he nearly fell down, so everyone pulled Clemont's Aipom Arm to pull Ash, Bonnie and Pikachu back up.
On the last day of the Pokémon Summer Camp, before the tournament began, Team Squirtle came to the cooks - who were the Team Rocket Trio - and were told they needed to hand over their Pokémon for health inspection at the Pokémon Center. Tierno gave his Squirtle, Shauna her Bulbasaur and Trevor his Charmander. After some time, Team Squirtle visited the Pokémon Center and were shocked to hear the cooks did not give her the Pokémon. The heroes joined Team Squirtle in finding the missing Pokémon. They found the cooks and Pikachu removed the table cloth, revealing Team Squirtle's Pokémon had been captured and binded by Leech Seed. Team Rocket removed their disguises and attacked with Inkay and Pumpkaboo. Clemont's Bunnelby used Dig, distracting Team Rocket and allowing Froakie to free the Pokémon by using Cut on the vines. Later on, Team Squirtle faced Team Froakie in a three-on-three battle. Squirtle used Rapid Spin to counter Pikachu's attack and soaked Serena's Fennekin with Water Gun. Fennekin tried to attack with Hidden Power, but was defeated by Squirtle's Aqua Tail. After Trevor's Charmander got defeated, Squirtle used Rapid Spin, but was pushed away by Clemont's Chespin's Vine Whip. Squirtle tried to attack with Aqua Tail, but was defeated by Pikachu's Thunderbolt, causing Tierno to lose, as well as Team Squirtle's defeat. Squirtle started crying, but Tierno held it, knowing Squirtle did its best. Later on, Tierno and Squirtle, per Ash's request, started dancing to train Ash before his match in Shalour City.
As Trevor spoke with the heroes, they recalled their first meeting in the Pokémon Summer Camp with Tierno and Shauna, as well as their Pokémon.
Once he met up with Ash, Serena and Bonnie, Tierno showed Squirtle has evolved into Wartortle. Unfortunately, Wartortle, along with its dancing partner Raichu and Ash's Sliggoo, were captured by Team Rocket. Sliggoo manages to help them escape by knocking the cage over a cliff and shattering it to pieces. Tierno and Bonnie arrived and found them, but when they confronted Team Rocket, they started a forest fire by accident. Sliggoo bravely used Rain Dance to douse the fire and surprisingly evolved into Goodra. Goodra then blasted Team Rocket off with its newly-learned Dragon Pulse move. Wartortle tag-teamed with Raichu in a double battle against Ash's Pikachu and Goodra. Wartortle got hit by Pikachu's Quick Attack and retaliated by using Rapid Spin. Goodra, who was hit by Raichu's Focus Blast and Charge Beam attacks, fired Bide. Wartortle tried to counter it by using Hydro Pump, but got hit by Pikachu's Iron Tail and thus, got hit by Goodra's Bide. Wartortle used Skull Bash to hit Goodra, who held Wartortle and launched it on Raichu. Using Dragon Pulse, Goodra, along with Pikachu's Thunderbolt, defeated Raichu and Wartortle.
When the heroes came to Anistar City for the showcase, they met up with Tierno and Shauna. Since Serena's Eevee was still shy, she had an idea and used it in a tag battle with Shauna's Ivysaur against Ash's Pikachu and Tierno's Blastoise, who evolved from Wartortle. Blastoise started with Rapid Spin, but the attack was countered by Eevee's Protect. Blastoise dodged Ivysaur's Razor Leaf, by using Tierno's dancing moves. Eevee tried to best Blastoise in the rhythm tactics, so Blastoise used Water Gun. Blastoise tried to use Skull Bash, but Eevee dodged the move and retaliated with Swift. Before the fight could continue, Serena canceled the battle, since she had an inspiration for Eevee's performances. Thus, Tierno continued the battle by fighting Ash, as his Pikachu's Thunderbolt was countered by Blastoise's Hydro Pump.
Blastoise was used during the quarter-finals of the Lumiose Conference. Tierno sent Blastoise out to battle against Sawyer and his Slurpuff, after his Raichu got infatuated. Slurpuff attempted to mesmerize it with Attract; however, Blastoise used its dancing strategy and deflected the move. It then defeated Slurpuff with a single Hydro Cannon attack. Blastoise then battled against Sawyer's Sceptile. Blastoise used Ice Beam, which got countered by Sceptile's Leaf Storm. Blastoise attempted to launch Hydro Cannon, but Sceptile avoided the attack and slashed him with Leaf Blade. To finish it off, Blastoise used Skull Bash, but was thrown in the air by Sceptile's Frenzy Plant. Before it was knocked out, Blastoise used Rain Dance to help Raichu have the advantage against Sceptile.
Due to chaos raging in Lumiose City, Tierno sent Blastoise to help him protect and escort the citizens to safety. Tierno's Blastoise was with his trainer at a Pokémon Center, where Tierno watched the broadcast about the Giant Rock.
Voice actresses and actors
- Megumi Hayashibara (Japanese as a Squirtle)
- Shin-ichiro Miki (Japanese as a Wartortle)
- Unshō Ishizuka (Japanese as a Blastoise)
- Michele Knotz (English as Squirtle)
- Billy Bob Thompson (English as Wartortle and Blastoise)
- ^ XY126: Valuable Experience for All!, Clemont mentions both Tierno and Blastoise being male
- ^ XY038: Summer of Discovery!
- ^ XY039: Day Three Blockbusters!
- ^ XY040: Foggy Pokémon Orienteering!
- ^ XY041: Battling Into the Hall of Fame!
- ^ XY043: Showdown at the Shalour Gym!
- ^ XY086: A Legendary Photo Op!
- ^ XY065: Good Friends, Great Training!
- ^ XY090: Tag Team Battle Inspiration!
- ^ XY126: Valuable Experience for All!
- ^ XY132: A Towering Takeover!
- ^ XY135: Rocking Kalos Defenses!
- ^ XY136: Forming a More Perfect Union!