Ash's Frogadier began as a Froakie known for its selective nature regarding trainers, returning to Professor Sycamore's laboratory multiple times after leaving or being returned by trainers it deemed unworthy. It preferred solitary training over socializing with other Froakie, causing friction within its group before encountering Ash. Observing Ash's bravery during a Team Rocket attack on Pikachu, this Froakie intervened to assist. Impressed, it later presented Ash with a Poké Ball at the lab, choosing to be caught voluntarily.

As Froakie, it showed protectiveness, attacking a wild Fletchling that upset Bonnie and Dedenne despite Ash's initial restraint. It learned the move Cut during this stage. Froakie evolved into Frogadier during a battle against Saizo's Barbaracle, gaining Aerial Ace upon evolution. This followed training with a ninja named Sanpei, where Froakie mastered Double Team after unsuccessful attempts to learn Quick Attack.

Frogadier developed a rivalry with Sawyer's Treecko (later Grovyle) after defeating it soon after evolving. Despite Grovyle evolving and learning Leaf Blade in a later encounter, Frogadier defeated it again using Water Pulse, intensifying their competition. Frogadier also had a complex relationship with Ash's Hawlucha; initial conflicts arose during double battles and training, including disagreements over combined move strategies. They resolved their differences after Ash protected them from an attack, leading to cooperation against Sawyer's Pokémon and searching for a wild Eevee.

Frogadier later evolved into Greninja during a mission to protect a ninja village. This evolution unlocked a unique synchronization phenomenon with Ash, known as Ash-Greninja, significantly enhancing its battle capabilities. Known moves from its time as Frogadier include Bubble, Water Pulse, Pound, Double Team, Cut, and Aerial Ace.