Li'l Kanga as a Mega Kangaskhan
Kanga and Li'l Kanga are X's first known Pokémon that he has ever since he was a small child. Years ago, they were used to win a Junior Tournament, which caused X to get the attention of the press. The constant attention eventually led to X shutting himself from society by refusing to leave his house and avoiding human contact. X's shut-in behavior had a negative effect on Li'l Kanga, who also refuses to leave her mother's pouch and never grew up into an adult Kangaskhan as a result. Since X refused to come outside, Tierno took care of Kanga in his stead.
In An X-cuse to Come Out and Play, Kanga is seen watching X's friends futilely try to get X to come out of his house. Later, X is attacked by Team Flare scientists Aliana and Mable, who demand that he give up his Mega Ring. Kanga attempts to protect X, but is injured in the process. The commotion causes Li'l Kanga to pop up from her mother's pouch and see her mother and Trainer being attacked. This angers Li'l Kanga, who reacts to X's Mega Ring and Mega Evolves into Mega Kangaskhan. The transformation allows Li'l Kanga to easily defeat Aliana and Mable's Pokémon, forcing them to retreat. Due to Vaniville Town being damaged in a battle between Xerneas and Yveltal, X and his friends are forced to travel while hiding from Team Flare.
In Inn-teresting Developments, the group arrives in Aquacorde Town, and X decides to camp out in a tent while Y and the others stay at an inn for the night. The inn turns out to be a trap set up by Team Flare, who attempt to keep Y and the others trapped inside the building while Aliana and Mable kidnap Li'l Kanga while X isn't looking. Y manages to escape and inform X of what is going on. X attempts to Mega Evolve Li'l Kanga to stop Aliana and Mable, but it doesn't work, so he instead teams up with Chespin to rescue Li'l Kanga and defeat the Team Flare scientists.
In The Aegislash Agenda, X and Trevor attempt to learn more about Mega Evolution by practicing against wild Pokémon, but their attempts to have Li'l Kanga transform end in failure. The group is then approached by Viola, who offers them sanctuary against Team Flare and assistance in finding out more about Mega Evolution. The group decides to accept and spends the night in Viola's Gym. There, X is challenged to a battle by Viola, which he accepts and wins with Kanga. Later that night, Celosia uses a mind-controlled Shauna to steal Kanga's Kangaskhanite while everyone else is sleeping. When everyone figures out what's happening, X immediately begins chasing after Celosia to get the Mega Stone back from her. He is assisted by Korrina, who has her Lucario Mega Evolve and help X fight Celosia's Aegislash. With Viola's help by holding Celosia down, X retrieves the Kangaskhanite and has Li'l Kanga Mega Evolve to help Korrina's Lucario. The combined might of the two Mega-Evolved Pokémon forces Celosia to run away.
In Pangoro Poses a Problem, Kanga and Li'l Kanga teamed up with Marisso and Salamè to battle the Lumiose Press editor-in-chief to protect Alexa. Kanga battles against his Pangoro and is unable to land an attack, so X Mega Evolves Li'l Kanga to fight as well, but the two are still unable to land an attack. Frustrated X attempts to get Marisso and Salamè to help, but notices they won't listen to him due to the editor's Spewpa's Rage Powder. The two eventually defeat the Spewpa and are left exhausted, allowing Pangoro to grab Marisso and Salamè with its paws. X then told Salamè to release his tail, which caused Pangoro's leaf to burn up. Without the leaf allowing it to sense what Kanga and Li'l Kanga were doing the two sent it flying out a window, defeating it.
In Pyroar Breathes, Kanga was used in X's attempt to break into Team Flare's hideout in Geosenge Town. While sneaking in Kanga used Mega Punch to defeat a Grunt's Noibat. Once inside Kanga teamed up with Élec and Garma to fight Lysandre's Mega Gyarados, Pyroar, and Mienfoo. Kanga ends up fighting his Pyroar and struggles due to the power of his flame attacks. Lysandre then questions why X hasn't Mega Evolved a Pokémon yet, only for a Mega Evolved Li'l Kanga to sneak up on Gyarados and attack, dealing a lot of damage. Lysandre then asks X if the sneak attack was worth it, and X reveals that he also choose to not Mega Evolve Élec due to his Lightning Rod Ability being used to drain Lysandre's machine's energy, allowing Xerneas to recover. Despite all this, X and his team are later seen defeated.
