This Froakie was first met in the first episode of the anime in Kalos, where it saves Pikachu from team rocket. in the fight Froakie was injured badly, and was taken to Professor Sycomore's pokemon lab, so as to be healed. whilst there, you learn that Froakie abandoned it's trainer as it did not like them. Later, Froakie helps Ash and Pikachu save Garchomp when it goes on a rampage. When they calm Garchomp down, Froakie decides to travel with Ash, and so Ash catches it.
In the anime, Serena chose this Fennekin after traveling to the professors lab from Vaniville town. They then travel to Santalune city where she meets Ash. On the way, Fennekin saves her from an angry wild pokemon.