Fennekin first appeared as one of the three starter Pokémon new trainers can choose from Professor Sycamore. Serena choose Fennekin as her starter Pokémon. Later on at the end of the fourth episode, a wild Vespiquen attacked Serena and Fennekin who mistook it as a person. But Fennekin protected her trainer by scaring it away with an Ember attack. Serena introduced her Fennekin to Ash, Clemont, Bonnie, and Pikachu. Eventually, Fennekin was used in its first Pokémon battle to help Serena to save Ash, Pikachu, and the Rhyhorn from Team Rocket.
Fennekin is a very friendly and kind-hearted Pokémon with a very bold heart. It tends to mimic Serena's actions as shown when it stretches like her at the same time. Fennekin is shown to take care in its appearance, as shown when it tries to tidy up its messy tail (after falling from Team Rocket's balloon), and does not let Pikachu, Froakie, Chespin and Meowth see, then thanks Froakie happily for helping it tidy up its tail. Fennekin can sometimes be very temperamental and would easily get angry without thinking when, for example, when it tried to hit Pikachu with Ember, it ended up hitting Ash instead. It can also get easily jealous over another person's Pokémon it being more cute and popular thanFennekin itself.