Ep. 125: A Timeless Encounter!

125

On the same day that Professor Burnet finds an old photo of Professor Kukui as a boy with a Litten and Ash and his Pokémon are training in the forest, Celebi turns up in Alola and accidentally sends Ash and Torracat back into the past, where they meet a very excitable (and familiar) boy with a Litten, whom Ash nicknames "Roary" and who is awed by Ash's battling ability. (Source: Wikipedia)