As a Tepig, being abandoned by Shamus, his original Trainer
As a Tepig, Pignite once belonged to a Trainer named Shamus, who abandoned him at the Accumula Town Pokémon Battle Club after losing to a Deerling in battle. Shamus was disappointed in Tepig and so, Tepig was tied to a post. When Don George tried to untie him, Tepig broke free of his bonds and began searching for his Trainer, but to no avail.
When Ash visited the Accumula Town Pokémon Battle Club in The Battle Club and Tepig's Choice!, Ash mistook Tepig for an Umbreon when watching a security tape of him stealing food from the nearby warehouse. In an attempt to capture the 'Umbreon', Ash then met Tepig for the first time when he was trying to eat some bait. He realized that Tepig was covered in soot and was unable to eat as there was a rope tied around his mouth, making him extremely hungry and very skinny. Initially, Tepig tried to run away, but after being cornered by Ash and having his rope removed and fed, he was carried back to the Battle Club by Ash. Later on, Tepig volunteered to help Ash retrieve his Pikachu from Team Rocket. Later, when Iris wanted to capture Tepig, he refused and decided he wanted to join Ash's team and Ash caught him in a Poké Ball.
Tepig was Ash's Pokémon during his first Striaton Gym battle in Triple Leaders, Team Threats!, against Chili and his Pansear, this surprised Iris, who thought he should have used a Water-type like Oshawott, Tepig hit with his Tackle, but it didn't do much to Pansear, but Pansear's Fire Punch did a lot of Tepig. Then Pansear's Flamethrower overwhelmed Tepig's Ember and then he took more damage of Dig. Tepig then ran around to dodge another Dig, but was then hit by another Dig. Pansear used Dig again but then Ash had Tepig jump into the hole and bite Pansear, when it emerged Tepig was biting Pansear's tail, though Pansear smashed Tepig into the ground, Tepig got up and still biting Pansear's tail, flung it around and then defeated Pansear with Ember and a Tackle attack.
Tepig was revealed to be male in Snivy Plays Hard to Catch! when he battled a wild Snivy that would eventually be caught by Ash. Although he managed to use an Ember attack, he was hit by the Snivy's Attract and became infatuated with her, causing him to be recalled.
In A Rival Battle for Club Champ!, he was used to fight against Trip's Tranquill. Like Oshawott before him, he was defeated by two consecutive Aerial Aces due to Tranquill's Super Luck Ability, which increased Tranquill's chance of inflicting critical hits.
In The Battle According to Lenora!, he battled Lenora's Lillipup, which promptly used Roar to force Tepig back into his Poké Ball. After Lenora's Watchog defeated Oshawott, he fought Lillipup again and was defeated. In Rematch at the Nacrene Gym!, he trained alongside Ash at Don George's Battle Club. He ran on a treadmill and dodged black balls that symbolized Shadow Ball attacks. By training, Tepig became faster and stronger, and learned Flame Charge. Later on, he battled against Lenora's Herdier, which soon used Roar to force Tepig back into his Poké Ball again. After Watchog and Oshawott knocked each other out, Tepig battled Herdier again and won because of his faster, stronger attacks and his newly learned Flame Charge move.
Tepig was Ash's first Pokémon for his Castelia Gym battle in Battling For The Love of Bug-Types!, he was sent out to battle Burgh's Dwebble. First he tried using Tackle on Dwebble, which was dodged easily and then a second Tackle was dodged by Dig, which hit Tepig. Dwebble then used X-Scissor which was very agile and hit Tepig. Burgh then explained that the rock Dwebble had on its back was lighter than normal, making it faster and more agile than normal Dewbble. Tepig used Ember, which was blocked by Protect. Afterwards he was hit by X-Scissor again. Tepig was able to hit Dwebble with Tackle and then went for a Flame Charge which was blocked by Protect. This lured Tepig up close and he was then knocked out by a super-effective close range Rock Wrecker.
Tepig was later used in Ash and Trip's Third Battle! to battle Trip's Vanillite. Tepig defended himself from Vanillite's Ice-type attacks with Flame Charge but could not keep up with some of its faster moves and despite the type advantage, the match ended in a tie.
Tepig was used in Gotta Catch A Roggenrola! to battle Roggenrola after Oshawott was defeated, only to be defeated himself. He later helped Ash rescue all of the Roggenrola from the Team Rocket trio. He later had a rematch with Roggenrola and after a fierce battle, he weakened it enough for Ash to catch it.
In Battle For The Underground!, Tepig was used to propel the train cart Ash and friends were riding on to get away from Team Rocket; along with Roggenrola using Flash Cannon and Axew using Dragon Rage. In the process, his Ember attack became Flamethrower.
With Shamus, upon evolution
In Lost at the Stamp Rally!, Tepig teamed up with Cilan's Pansage when his Trainer Ash and Cilan battled against Subway Bosses Ingo and Emmet. Battling their Eelektross and Chandelure, Tepig and Pansage battled well but were eventually defeated.
In Evolution by Fire!, while eating with the other Pokémon in the Battle Club, Tepig recognized his previous Trainer, Shamus. Upon seeing him, Tepig happily ran over to Shamus, believing that he would be happy to see him. However, when Shamus threw Tepig at Ash and called him a useless Pokémon, he was very disheartened. Being angered by Shamus's actions, Ash accepted Shamus's challenge of a Double Battle, pitting Tepig against his former Trainer's Emboar and Heatmor the next day. That night Tepig sat alone outside the Battle Club and got very upset while recounting his abandonment. Snivy slapped him with Vine Whip and talked sense into him, as they were preparing for the battle in the morning. Despite Snivy's encouragement, when faced with battling his estranged Trainer, he froze up and was unable to launch any attacks. Though Tepig had thought that abandoning him was a very hard thing for Shamus to do, he was crushed when Shamus revealed he was relieved to get rid of him. However, after watching his friend Snivy take two powerful hits when she was distracted with encouraging him further, Tepig finally hit both of his opponents with a powerful Flame Charge. However, Emboar and Heatmor were able to take the attack and on Shamus's command launched a Flare Blitz/Fire Spin combination move. Making no attempt to dodge, Tepig was pushed out of the way of the attack by his partner Snivy, who took major damage and was knocked out. Tepig became as motivated as his Trainer and Snivy continued to show faith in him, as he evolved into Pignite. With his new power, Pignite used Fire Pledge, impressing both his former and current Trainer and dealing major damage to Emboar and Heatmor. With a final Flame Charge attack, Pignite was able to knock out both of his opponents. After the battle, Shamus talked to Pignite, saying he was impressed with his new power, and asked him to rejoin the team, but Pignite refused, scorching his previous Trainer's face with a Flamethrower and sending him running away in anger.
In Caution: Icy Battle Conditions!, Pignite battled Brycen's Cryogonal. The match started with Pignite's Flame Charge being blocked by Reflect and his Flamethrower being deflected by Rapid Spin dealing damage to Pignite as well, making Pignite unable to hit the speedy Cryogonal. After enduring Cryogonal's Frost Breath, Pignite was able to land a direct hit with Fire Pledge, hitting Cryogonal's Rapid Spin in the centre and knocking it out. Pignite next went up against Brycen's Beartic where his Flame Charge was stopped by Beartic's Brine which was super-effective. Pignite then took out a powerful Icicle Crash and then an unavoidable Aerial Ace which was also super-effective.
In Rocking the Virbank Gym! Part 2, Ash sent out his Pignite as his fourth Pokémon during his Gym battle with Roxie, facing her Scolipede. Despite her part Bug-type Pokémon being at a type disadvantage against Fire types, Roxie stood calm. Pignite started by trying a Flame Charge, which was blocked by Scolipede's Screech. The Megapede Pokémon next attacked with Sludge Bomb, which was also blocked by Pignite's Flamethrower, causing a big explosion and a cloud of smoke. Using the smoke to his advantage, Ash had Pignite use another Flame Charge, hitting Scolipede and dealing a lot of damage. As Pignite tried to finish the match with another Flamethrower, Scolipede dodged and used Toxic on Pignite, badly poisoning him. However, Pignite was able to go on and unleash a Fire Pledge on Scolipede, defeating it. Roxie then gave Pignite a Pecha Berry, curing him of the poison before sending out her strongest Pokémon, Garbodor. The Trash Heap Pokémon was able to use its extendable arms to dodge Pignite's Flame Charge before hitting the Fire Pig Pokémon with Double Slap and doing the same again to dodge a Flamethrower. Pignite then used Tackle on Garbodor's arm, causing it to fall over. Pignite was about to use Fire Pledge, but Garbodor extended its arm under his hand, preventing him from using the move, grabbing him, and tossing him to the floor. After getting hit by a few Double Slap attacks, Pignite was finally able to unleash his Fire Pledge attack, but Garbodor countered with a Hyper Beam, which went right through Fire Pledge and hit Pignite, knocking him out.
In Ash, Iris and Trip: Then There Were Three!, Pignite battled Trip's Serperior in the Pokémon World Tournament Junior Cup finals. Even though Pignite battled hard, had a type-advantage and managed to dodge many of his opponent's attacks, Serperior was too fast and dodged every single one of Pignite's attacks, as well as landing a direct hit with Solar Beam. In the end, he became tired and was finished off with a powerful Frenzy Plant.
In Cameron's Secret Weapon!, Pignite was the third Pokémon Ash used in his Vertress Conference battle against Cameron, sending him out against his Hydreigon which had already defeated Boldore and Oshawott. Pignite started the battle with his new Brick Break attack, which was super effective against the Dark/Dragon-type Pokémon. Hydreigon countered by attacking with Dragon Pulse, which scored a direct hit. After narrowly dodging Pignite's Flamethrower, the Brutal Pokémon scored a pair of powerful hits with a Tri Attack and a Dragon Rush. Despite of this, Pignite was still able to fight back, and served his own pair of powerful strikes with Brick Break and Flame Charge, before dodging Hydreigon's Double Hit-counterattack. Next Pignite used Fire Pledge, forcing Hydreigon to take flight in order to avoid it, allowing him to land a direct hit on it with a Flamethrower. Ash then commanded Pignite to serve the finishing blow on his weakened opponent with Brick Break. Although Hydreigon tried to counter with a Double Hit, Pignite easily avoided it and served the super effective strike on the Brutal Pokémon, finishing it off. Cameron's next Pokémon was Ferrothorn. After avoiding Ferrothorn's Metal Claw, Pignite was hit by a Pin Missile. Despite the fact that Pignite was starting to get weak, he was still able to fire a super effective Flamethrower on the Grass and Steel-type Pokémon. Although Ferrothorn tried to attack back with Mirror Shot, Pignite was easily able to dodge it and strike with Flame Charge, finishing the Thorn Pod Pokémon. Cameron then sent out his third Pokémon, Samurott. Pignite stood no chance against the Formidable Pokémon, which first countered the Fire Pig Pokémon's Flamethrower with a super effective Hydro Cannon, and then knocked him out with an equally powerful Aqua Jet.
He was sent out to battle Barret's Magnezone in Secrets From Out of the Fog!. Despite having the type advantage, Pignite was soon defeated by a Magnet Bomb attack that also rebounded Pansage's Bullet Seed attack at him. It was soon discovered in the next episode that the reason Pignite was so easily defeated before was because of a Bullet Seed pellet getting lodged up his nose and preventing him from using his Flamethrower attack. After Ash had Charizard throw Pignite about to get it out, to no avail, Iris tickled Pignite's nose with some grass and he sneezed it out.
Later in Team Plasma and the Awakening Ceremony!, Pignite was sent out alongside the rest of Ash's team to help Ash and N dig up to the surface of the White Ruins. While battling Team Plasma again, Pignite became very concerned for Charizard who had endured several Shadow Ball attacks and came to its rescue by stopping the Liepard's attacks with Flamethrower. The two then launched an incredibly powerful double Flamethrower at Team Plasma's Pokémon. However, when Colress turned his mind control machine on them, Pignite was quickly recalled to his Poké Ball along with Ash's other Pokémon.
In The Journalist from Another Region! he participated in the Pokémon Sumo Tournament of Harvest Island's Grand Harvest Festival. Pignite managed to get to the finals by beating a Watchog rather easily with a push, a Slaking; winning by default as the Lazy Pokémon was sleeping, and a Rhyperior. He and Ash then faced Rodney and his Golurk. He defeated the Golurk when it lunged itself towards Pignite, giving him the power to throw the Automaton Pokémon over his head and out of the ring, winning the tournament and a year's supply of fruit as a prize as well as a Focus Band, which Ash proudly gave Pignite to wear.
Pignite was reunited with the entire Unova team at Professor Oak's Laboratory in The Dream Continues!. He joined the others in a group attack on Team Rocket with his Flamethrower to send them blasting off for the last time in the Best Wishes series. Pignite later posed in a group photo with the rest of Ash's Pokémon. Then, he was left at the lab when Ash set off for the Kalos region.