A Trip Down Memory Train! (Japanese: 追憶のトレイン！シトロンとホルビー！！Memories of the Train! Citron and Horubee!!) is the 88th episode of the XY series, and the 887th episode of the Pokémon anime. It first aired in Japan on September 17, 2015, in Canada on October 31, 2015, and in the United States on November 7, 2015.
On the road to Anistar City, Ash and friends fall into a Team Rocket pit trap! Pikachu quickly sends the villains blasting off again. Then the ground underneath our heroes collapses, leaving them in an abandoned subway tunnel.
Bonnie is reminded of when she and Clemont first met Bunnelby, who was living in an old subway car in Lumiose City with a group of Pokémon. The group was being threatened by a grumpy Diggersby who wanted the train for itself! Thanks to some battling tips from Clemont, Bunnelby managed to defeat Diggersby and protect its home.
Soon after, the subway car was in danger, and Clemont, Bonnie, Bunnelby, and all its Pokémon friends—now including Diggersby—had to work together to move it to safety! After the train found its new home, Clemont and Bunnelby sadly parted ways...but Bunnelby’s friends had a better idea. They encouraged Bunnelby to go after its newly chosen Trainer, and the rest is history!
While still travelling towards Anistar City, Ash and his friends fall down a deep hole. As the heroes are okay, they look above to see Team Rocket, who gloats about digging this pitfall trap and wants to get Pikachu. To teach their foes a lesson, Ash has Pikachu attack with Thunderbolt but Meowth releases a net that cancels electricity. Clemont sends Bunnelby to break the net with Mud Shot which allows Pikachu to use another Thunderbolt and Team Rocket gets blasted off. As the heroes celebrate, they fall down into a much deeper hole and land into an abandoned mine.
Pikachu notices train tracks and Clemont points out that they should follow the tracks to get out. As they walk, Bonnie tells Clemont that this has happened to them before when they first met Bunnelby. Ash and Serena ask Clemont to tell them how they met each other and Clemont tells them the story. Clemont's story begins after he was thrown out of the Lumiose Gym by Clembot, where he is trying to figure out how to get back in. Bonnie runs towards to Clemont and hands over an apple, the only food she could find in the house. Suddenly, a Bunnelby snatches the apple off Clemont's hands, and Clemont and Bonnie chase after the Bunnelby.
Clemont and Bonnie notice Bunnelby jumping over a barrier. The two follow it over the barrier but then realize they have jumped into a deep hole. The two land with a crash into an abandoned subway tunnel. Clemont decides to forget about the Bunnelby and takes out a subway map to focus on getting out. The two head west and eventually reach an old, but well preserved station. At that point, Clemont and Bonnie sees Bunnelby heading into a train carriage, where it is greeted by Patrat, Trubbish, Delcatty, Skitty and Zigzagoon. Bunnelby cuts the apple into slices and the Pokémon happily eat it. Seeing all this, Clemont realizes Bunnelby took the apple to help the other Pokémon. Bonnie asks why the Pokémon are living here, and Clemont answers that this place keeps them dry and warm regardless of the weather, which is important for city dwelling Pokémon.
Suddenly, a Diggersby approaches and kicks Bunnelby and the other Pokémon out. Bunnelby faces the Diggersby and the two each attack with Mud Shot. However, Diggersby's Mud Shot is stronger and lands on Bunnelby. Diggersby is about to attack with Hammer Arm when Bunnelby counters with Double Slap. Next, Bunnelby uses Dig to get behind Diggersby, but Diggersby counters with Super Fang. Bunnelby then uses Double Team but Diggersby successfully attacks Bunnelby using multiple Double Kick. Bonnie pleads for Clemont to help, but he is helpless with all his Pokémon back at the gym. Just as Diggersby's Mud Shot is about to land, Clemont uses his Aipom Arm to withdraw Bunnelby to safety. However, Diggersby attacks with Mud Shot causing Clemont, Bonnie and the Pokémon to run away.
Despite his expertise being in Electric-type Pokémon, Clemont heals Bunnelby using a Super Potion and bandages its ear and arm. Immediately, Bunnelby wants to fight the Diggersby again. Bonnie exclaims that her brother is the Lumiose City Gym leader and all the Pokémon gasp in surprise. Clemont then tells Bunnelby that it needs to use strategic battling not brute force when dealing with a stronger opponent. However, Bunnelby doesn't understand Clemont's advice and so Bonnie decides to act it out. Bonnie acts as Diggersby and Clemont acts as Bunnelby to show how to evade Hammer Arm with Dig and use its ears as a defense.
After some special training, Bunnelby challenges Diggersby. Diggersby uses Hammer Arm while Bunnelby dodges with Dig, causing Diggersby to stumble into a pole. Diggersby uses Mud Shot and Bunnelby again dodges with Dig. Diggersby attacks down the hole with Mud Shot but Bunnelby jumps out of the hole before the attack lands. When Diggersby uses Super Fang, Bunnelby evades with Double Team, and then uses its ears to lift a stone tile as Diggersby charges into it. Diggersby then tries to land a Double Kick, but Bunnelby stops it with its ears. Bunnelby then sends Diggersby flying towards a wall using Double Slap. Surprised, Bunnelby runs off to Diggersby and offers to make peace. However, Diggersby refuses and runs away ashamed. Bonnie then exclaims that Clemont and Bunnelby are a great team.
At that point, the station begins to crumble as it is being demolished. However, since none of the Pokémon want to leave their home Clemont decides to move the train to a safer place. Using his invention, the "Running Generator", Clemont powers the train with electricity by having Bonnie and the Pokémon run on the treadmill. But before they begin, a large rock descends from the ceiling and blocks their path. Just then, Diggersby returns and removes the large rock before making up with Bunnelby. As the station continues to crumble, Clemont drives the train out. At a junction, the subway map informs them to turn right, however, the train tracks are headed left. Bunnelby quickly fires a Mud Shot at a switch and changes the direction of the tracks. Soon they exit the subway and end up at another abandoned but overground station. Clemont claims it is safe here because there are no plans for reopening or construction.
Clemont and Bonnie leave, but Bunnelby appears crestfallen. Delcatty and the other Pokémon urge Bunnelby to go off to Clemont, with Diggersby reassuring Bunnelby. Bunnelby runs off and meets Clemont.
The scene cuts back to Ash and his friends and Ash exclaims that Bunnelby was Clemont's first Pokémon that was not an Electric type. At that point, Bonnie points out that the tunnel is a dead end. Clemont orders Bunnelby to use Dig, causing the rubble to fall away. They then exit the tunnel, but Bonnie tells Clemont that he didn't finish the story. Bonnie finishes the story by telling them that Clemont cried profusely in joy after catching Bunnelby. Clemont becomes angry and rebuts that Bonnie is exaggerating and that there was no crying.