Lost at the Stamp Rally! (Japanese: サトシ、デントVSサブウェイマスター！Satoshi, Dent VS Subway Masters!) is the 51st episode of the Best Wishes series, and the 708th episode of the Pokémon anime. It first aired in Japan on October 6, 2011 and in the United States on March 3, 2012.
As Ash and the gang wait for the bridge to Driftveil City to be repaired, they decide how they’re going to spend their day. Cilan excitedly announces he’s going to participate in the Subway Bosses Stamp Rally, which will allow the winner to have a battle with one of the Subway Bosses, Ingo and Emmet. But to win, he must obtain 60 Pokémon stamps by that afternoon—a challenge that usually takes three days to complete!
Ash and Iris decide to head out for a day of sightseeing. After visiting the two sports arenas and the Musical Theater, they end up in the amusement park, where they find a lost female Axew who’s been separated from its Trainer, Erina. They try to help out by going back to the subway station where Axew and Erina were to meet. But when they arrive, Erina is nowhere in sight.
Iris leaves a note for the lost Axew’s Trainer, telling her that they will be back at the amusement park. In the meantime, Erina runs into Cilan during the stamp rally, and he eventually leads her back to the station to find the note from Iris. Then, with the aid of the Subway Bosses, Erina and her Axew are happily reunited!
Time is called for the stamp rally, and Cilan realizes that he’s missing just one stamp to win. As thanks for his help, Erina gives Cilan the stamp he needs—and out of the kindness of their hearts, Ingo and Emmet offer to have a Tag Battle with Cilan and Ash, much to our heroes’ excitement!
A fierce battle ensues at Gear Station, and Ingo and Emmet are victorious. Despite the defeat, our heroes are grateful for the opportunity to battle the amazing Subway Bosses, who tell them the bridge has been repaired and they can leave for Driftveil City whenever they want. But they decide to stay one more night for the chance to ride Nimbasa City’s famous Ferris wheel. We leave everyone as Ash starts to turn his eye toward his upcoming Gym Battle at the Driftveil City Gym...
After his victory against Elesa at the Nimbasa CityGym, Ash and his friends spend more time in Nimbasa City while the drawbridge is being repaired. Ash and Iris run after Cilan as the latter races to the subway station. When pressed for an explanation, Cilan tells Ash and Iris that the Nimbasa City subway stamp rally is finishing that day, and he wants to be a part of it so that he can battle against either Ingo or Emmet. Although Ash expresses an interest in competing as well, he has already promised to spend the day with Iris.
Leaving Cilan alone to do his stamp collecting, Ash and Iris excitedly go to see several different events in Nimbasa City - they attend a sports event between the Gurdurr 11 and Team Darmanitan, play a game of tennis at the Small Court, and go to see a Pokémon Musical show that involves Ash, Oshawott, and Pikachu being pulled onto the stage to dance with the performing Pokémon. As Iris races ahead to go to the Ferris wheel, Ash loses sight of her and sees an Axew, which he mistakes for Iris's before noticing the bow on her tail. After that, Iris arrives and surmises that the Axew is lost, and she and Ash decide to try and find Axew's Trainer.
Meanwhile, Cilan has made significant progress in his quest to collect every stamp within the time limit, when a girl approaches him and asks for directions to the amusement park. After giving her directions, Cilan resumes his task. Ash and Iris enter the subway, still looking for Axew's Trainer, when the female Axew spots what she believes to be her Trainer and runs onto the subway, leaving Ash and Iris to try and find her. While looking for his final stamp, Cilan sees the same girl that he helped earlier and introduces himself. The girl tells him that her name is Erina and she explains that she and a friend were separated on their way to the amusement park. Cilan then happily agrees to help Erina find her way back so that she and her friend can reunite with each other. Suddenly, as the express train that Ash and Iris are on passes the platform where Erina and Cilan are standing, Erina spots the female Axew on the express and cries out as she realizes where her friend is. Axew had mistaken a girl with a Swadloon for her Trainer, and the resulting pandemonium ends up with everybody in the car being shocked by Emolga's Discharge.
After leaving the express train, Ash and Iris apologize to a staff member for their conduct on the train and then try to figure out how to find Axew's Trainer. They agree to go back to the amusement park after leaving Axew's paw print at the stamp area so that her Trainer will see it and figure out where Axew is. Not long after, Erina and Cilan arrive at the same spot and correctly interpret the message Ash and Iris left behind. However, Cilan realizes that he accidentally led Erina in the exact opposite direction of where they should be heading and are in fact traveling away from the amusement park.
As Ash and Iris stand outside the subway entrance, a man who works at the subway runs out and asks if they are Ash and Iris before bringing them to another train bound for Nimbasa Central Station. While on the platform at the station, Axew spots Erina and the two of them share a happy reunion. Much to Ash's surprise, Cilan walks up, accompanied by Ingo and Emmet. When Iris queries about Cilan's progress in the stamp rally, Cilan begins to panic as he realizes that he has yet to acquire his Axew stamp. Unfortunately, the contest ends at that precise moment, leaving Cilan one stamp short. As Cilan laments the loss of his childhood dream, Erina offers him her Axew stamp, and Ingo and Emmet agree to have a battle with Cilan and Ash.
The battle begins with Emmet's Eelektross and Ingo's Chandelure against Tepig and Pansage. The battle gets off to a quick and very heated start, with fierce attacks and combinations from both teams. Although Pansage and Tepig display impressive combination attacks, Ingo and Emmet emerge victorious from the battle. That evening, outside the subway station, Ingo informs them that the Driftveil Drawbridge has been repaired. Before going to sleep at the Pokémon Center, the group takes a ride on the Ferris wheel and Ash excitedly anticipates his upcoming battle in Driftveil City.