To Thine Own Pokémon Be True! (Japanese: ポケモンピンポン大会！エテボースがんばる！！ Pokémon Ping-Pong Competition! Do Your Best, Ambipom!!) is the 20th episode of Pokémon: DP Galactic Battles.
Ash and Pikachu already come out of the Center for the Ping-Pong Tournament and Barry follows them. Dawn and Brock come out, though Dawn does not understand rules even a bit. Barry explains that the trainer teams up with its Pokémon and play - trainer uses the paddle, while the Pokémon the body itself. The trainer serves, and once they got eleven points, the team wins a game and winning three games declares the trainer a winner. So, they go to fill out the papers; Ash sides with Pikachu and Dawn with Ambipom, meaning Piplup stays with Brock.
Ash and Dawn agree to have a bit of warm-up. Ash calls heads and Dawn tails, so Dawn uses her Pokétch and the result is tails, so Ash serves. As they play, a man passes. Ambipom hits the ball very hard and goes to the man, but the man gets the ball. Dawn apologizes to the man, though the man is impressed by Ambipom's strike. He advises Ash and Dawn to continue playing like that and not to lose focus. Brock sees on a front of a magazine the man who just went away. They all proceed with Barry inside. They see Ash and Dawn will have to compete each other soon, while Barry will not. They spot the man is also competing, shocking Barry they do not know his name. Barry tells them the man is O, a powerful Ping-Pong Champ who is seeking for trainers and Pokémon to compete. Barry advises to Ash to give his best to show the man who is stronger.
The signal is given and the audience gathers. James (disguised) sits next to Brock. Brock, unaware of James being disguised, tells that his friends are competing. James admits is friend is doing as well, so they now see how much in common they have. The announcer displays the winners will get Pokémon food and solid gold Ping-Pong balls. Meowth is dazzled by the prize, but Jessie hushes him, as he must not speak or the twerps will discover them. The Tournament begins; Ash shakes, but makes it known to Dawn they are here to have fun. Dawn warns him he is holding a fan, not a paddle. Jessie argues with the judge as Marowak holds a club, while Meowth cannot hold the paddle. Meowth has a plan, so Jessie agrees to the rules.
The Pokétch decides Marowak and the trainer to be first. Meowth uses Fury Swipes, cutting the ball. However, using moves is illegal, meaning Jessie and Meowth get disqualified. Ash and Pikachu battle a trainer with Farfetch'd. Ash soon discovers a strategy, but gets hit by a ball. Dawn and Ambipom face a trainer with Alakazam. Though Dawn and Ambipom hit the ball back, Alakazam's spoons make it unclear to Dawn with which one will it hit, and the opponent gets a point. The game restarts and Alakazam hits the ball with the spoon, but Ambipom hits it back with the tails. Though the opponent hits it back, Ambipom hits with increased speed, getting Dawn a point.
The Tournament continues, as the trainers and Pokémon play the Ping-Pong. Jessie is angry as they lost in the first round, so demands a robot to get the prize by force. Meowth responds they have no money, so Jessie calls him useless and goes away. Ash and Pikachu lost in the first round and join Brock and James. Ash feels he let Pikachu down, even if it is his first time, but Dawn and Ambipom are working great. Dawn and Ambipom face the opponents Jessie and Meowth did. Though very hard, O sees them and doubts they are playing for the first time. The opponent hits the ball hard and Dawn would've lost... but Ambipom hits the ball before it reaches the ground. Marowak cannot handle such a fast ball and loses its club, meaning Dawn and Ambipom won. Jessie thinks if she had held Ambipom when she was an Aipom that Jessie saved her life, she would've won.
Dawn and Ambipom made it far. Now it is Barry vs. O. While Barry hits the ball O missed, Shiftry comes and hits the ball and gets a point for O. Eventually, O and Shiftry win. Now it is Dawn vs. O. Though keeping valiant, Dawn and Ambipom cannot face someone fast as Shiftry. Dawn tries to keep calm, and with Ambipom's fighting spirit, continues the match. Shiftry strikes the ball and Dawn counters it, but this causes her paddle to be broken, so Ambipom continues in her stead, making O nervous. Eventually, she manages to win, so Dawn takes another paddle and works with her. O is impressed, but swears he will win.
Later, Dawn and Ambipom lost, as Ambipom was exhausted. Nurse Joy treated her and tells she needs rest. Dawn apologizes to Ambipom for letting her do most of the work. O is impressed and wants to train one of the greatest Ping-Pong competitors. Dawn explains she is after the Contests, but O meant Ambipom and wants her to take. Dawn does not know about this. The night, Dawn is scared as she cannot fin Ambipom, so Ash and Brock go to find her. They hear a noise - Ambipom is training. While Dawn sees her happy, she is unsure to give her, so asks Ash what should she do. Ash tells her that it is important what Ambipom wants, while Brock reminds that it is the trainer's job to make sure to respect what the Pokémon wants.
As O is going away, the gang manages to talk to him before departing. Dawn decided to give away Ambipom if she wants. Ambipom takes the Poké Ball, Ping-Pong Ball, Ash's hat and Dawn's hat and tosses them, then thinks a bit. Ambipom has decided - she leaves the Poké Ball to Dawn, meaning she decided to go after Ping-Pong Tournaments. O is pleased by the result and tells them that he is working in Vermilion City in Kanto and offers them to come there whenever they want to. Ash and Dawn wish Ambipom luck and she departs with O. The heroes an Ambipom wave hands at each other for goodbye.
- Professor Oak's Pokémon lecture: Happiny
- An instrumental version of A Small Thing is used as background music.
- The ending animation receives a minor change in this episode, as the Pikachu-colored Pichu is now surrounded by sparkles when it first appears similar to the games when a Shiny Pokémon enters a battle.
- The dub title is based on a well-known quote To Thine Own Self Be True, from William Shakespeare's Hamlet.
- As Dawn is waiting in the hall of the Pokémon center, the Generation I healing music is heard before Nurse Joy exits the operation room.
- This episode shares some similarities with The Punchy Pokémon:
- A main character participates in a special Contest, using a monkey-based Pokémon.
- The main character ends up giving his/her Pokémon that participated the Contest to be trained for another participant of the Contest.
- During the match between Dawn and Halverson, the end of Marowak's bone is colored brown instead of white.
- During the match between Dawn and Halverson the score board states Halverson is winning the games 10-9 over Dawn, however when Dawn wins just one rally she also wins the game which is impossible due to a person only scoring one point at a time.
- In O's match against Dawn, in one scene, O was winning 10-6, but when Dawn breaks her paddle, O was winning 9-7.