Garchomp is Ritsu's third Pokemon she caught in Full Moon's Full Pokemon Journey. She debuted as a Gabite in Chilling The Twin Trouble when she went havoc and attacked the Light Music Club, but she lost to Tsumugi's newly-evolved Vanilluxe, allowing Ritsu to catch it.
She appeared again when she helped Ritsu carry some supplies that she bought. She was later confirmed female in the second season. She evolved into Garchomp during a battle against Team Rocket and learning Flamethrower in the process, she maintained her loyalty to Ritsu, which was shown when Ritsu hugged her for the win.
In "What's In a Nickname?", she was officially nicknamed Garcha by Ritsu, and even nicknamed the other Pokemon she has owned.
Garchomp's known moves are Dragon Pulse, Crunch, Flamethrower and Dragon Claw, and her ability is Sand Veil. As Mega Garchomp, her ability is Sand Force.