Evolution by Fire! (Japanese: 炎のメモリー！ポカブVSエンブオー！！ Flaming Memories! Tepig VS Emboar!!) is the 29th episode of Pokémon: BW Rival Destinies.
After foiling another Team Rocket plan and passing through Twist Mountain, Ash and co. stop off for the night at Don George's Pokémon Battle Club in Astilbe Town. At the battle club, Tepig walks up to its former trainer, a boy named Shamus. He is the previous owner of Ash's Tepig due to Shamus abandoning Tepig because he believed that it had no talent for battles when it lost to a Deerling but he never cares when he lied. When Ash went to get Tepig, Shamus said that he was glad to give up such a little runt of a Pokémon for its little talent as he finds another Tepig with a little less talent, which enraged Ash after he put two and two together. So Ash is challenged to a Double Battle against Shamus' Emboar and Heatmor: "The Fire Warriors" to prove how useless Tepig is. Can Tepig really prove that his talents are worth anything?
The heroes wander to Icirrus City. To stay for the night, they go to Pokémon Battle Club. As they walk through the halls, they hear some sounds. They enter a room, in which two trainers have a battle. Mienshao uses Drain Punch on Heatmor, while Watchog slams Emboar to the ground. However, his opponent grins, ordering his Pokémon to show the power of "the Fire Warriors". Emboar uses Hammer Arm on Watchog and Mienshao, while Heatmor's Flame Burst defeats them. Don George declares the opponent, Shamus, to be the victor, which Ash admits they are a tough team. The heroes admit that was one fine battle. However, they spot Shamus with the trainer he fought.
Shamus intimidates the trainer, wanting the Pokémon, for he did not have the battle for nothing. The heroes tell Shamus he is not allowed to take other people's Pokémon if they lost. Shamus replies them to back off. Don George praises Shamus's battle skills, though Shamus leaves. The trainer thanks them, claiming Shamus actually wanted to battle so he can take Pokémon "with potential". As the heroes have dinner, Tepig turns around and sees Shamus. Tepig remembers something, then comes to Shamus, trying to take his attention. Cilan sees Tepig is liking that trainer. Iris reminds Ash Tepig was abandoned by its original trainer, so Ash suspects Shamus is Tepig's original trainer.
The heroes come to Shamus and express their findings. Shamus confirms that, so Iris yells at him for abandoning his own Pokémon. Shamus replies he thought that was the best, so Ash and Iris demand an apology from him to Tepig. Shamus refuses, so Cilan dresses as a judge to determine the judgement of Shamus' act. Ash expresses Tepig was abandoned and had a hard time living without his master. Iris yells Shamus must be punished, but Cilan calms her down, else he'd have to remove her. Shamus replies he saw Tepig was weak and had left him, otherwise Tepig would just lose battles. Ash asks why was Tepig tied up. Shamus responds Tepig was following him and he had to tie him up. Iris yells it is cruel not to reveal a Pokémon's talents when it is young. Cilan admits these are all good points.
Don George appears, replying they should battle to see who is wrong. Shamus advises a Double Battle against Tepig, though Snivy comes, wanting to battle as well. Cilan reminds them Snivy was also abandoned by a trainer, so Ash accepts her in the battle. Don George announces the battle will take place tomorrow morning, though Ash and Shamus are determined to prove each other wrong. Tepig, however, is scared. During the night, Tepig walks out and remembers Shamus released him and despite Tepig's wishes, Shamus binded him and walked away. The heroes come to Tepig and Ash proposes training. Tepig does not want to, so Cilan thinks Tepig has not gotten over Shamus yet. Iris is surprised, telling Tepig is just too nice. Snivy approaches Tepig and slaps him with Vine Whip, managing to persuade Tepig to battle Shamus.
Next day, Shamus and Ash have the battle. Ash sends Tepig and Snivy, while Shamus his Heatmor and Emboar, though Ash sees Tepig is still sad. Snivy uses Leaf Storm on Emboar, who deflects the attack. Ash orders Tepig to use Flamethrower, but Tepig remembers Shamus before departing and fails, then gets hit by Emboar's Hammer Arm. Ash feels Tepig did not forget about Shamus being his trainer. Shamus laughs, for he showed Tepig that a bit of emotion, but when he left Tepig's sight, was actually relieved Tepig is not with him. Tepig is crushed by these words, so Ash asks Shamus does he actually call himself a trainer. Shamus replies he only wants a Pokémon with some skill, so Ash is determined to show Shamus what a real battle looks like.
Iris and Cilan worry, for Tepig is too sad to fight and the Fire Warriors may use combination attacks to defeat the opponents. Snivy tries to get some sense into Tepig, but fails, so Ash tells she should cover Tepig instead. Snivy manages to attract Emboar, hitting him with Vine Whip. Heatmor use Fury Swipes on Emboar, whose Attract effect wears off. Emboar uses Flamethrower and Heatmor Fire Spin. Snivy dodges the attack, but Tepig is too depressed to dodge and takes the hit. Snivy gets hit by Heatmor's Fury Swipes and Emboar's Heat Crash. Emboar leaves, though Snivy still stands up and yells at Tepig. Tepig gains confidence and attacks Emboar and Heatmor with Flame Charge.
Shamus admits Ash raised Tepig well, but it is still not good enough. He considers if the opponent is not taken down hard enough, it is considered as a third-rate battle. Emboar uses Fire Blitz and Heatmor Fire Spin, which mold together. The attack is aimed towards Tepig, but Snivy tackles Tepig, causing herself to be the target. The attack proceeds and Snivy is immediately defeated. Ash goes to call Snivy back, but Snivy wants to see Tepig battle. Ash lets Tepig know everyone is supporting him. Tepig is very determined and evolves into Pignite. Shamus thinks even if Pignite evolved, he'll never defeat Emboar.
Pignite uses Fire Pledge, which hits Emboar and Heatmor, shocking Shamus. With Flame Charge, Pignite defeats Emboar and Heatmor. The heroes are pleased about Ash's victory and Pignite hugs Ash and Snivy for believing in him. Shamus congratulates Ash on the victory and apologises to Pignite for doubting his skill. However, Shamus proposes to Pignite to abandon Ash to reach the top. Pignite looks to Shamus and burns him with Flamethrower, for he wants to stay with Ash. Enraged, Shamus runs off, while Ash is glad Pignite trusts him.
- This episode is similar to Charmander - The Stray Pokémon, for Damian, like Shamus, abandoned Charmander, considering it weak. Both came back to invite them back, but were instead hit by Flamethrower.
- Who's that Pokémon?: Heatmor (US).