After foiling another Team Rocket plan and passing through Twist Mountain, Ash and co. stop off for the night at Don George's Pokemon 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's 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 worthless Pokemon 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's Emboar and Heatmor:"The Fire Warriors" to prove how useless Tepig is. Can Tepig really prove that his talents are worth? Yes.
Shamus' Emboar is confirmed to be male.
This is the second time Ash looked up Pignite on the Pokedex. First was BW013: Minccino-Neat and Tidy! but the difference is it didn't say "the evolved form of Tepig".
In the flashback, it is revealed that Shamus was replacing his own Tepig in Accumula Town for another one before Ash and co. (minus Cilan) even arrive here. Which made Tepig feel heartbroken during the battle against him.