A Marathon Rivalry! (Japanese: 燃えよカビゴン！ポケスロンの王者！！ Get Fired Up, Snorlax! The Pokéthlon King!!) is the 3rd episode of Pokémon: DP Sinnoh League Victors.
As the heroes continue their path to Daybreak Town, they spot a giant trampoline. Pikachu and Piplup jump on it and get bounced when a Snorlax jumps on it as well. They notice Snorlax is much stronger and a man comes, seeing that Snorlax improved. The man is a scientist named Daniel and the heroes introduce themselves to him. Daniel brags that he used scientific methods to train it. In his facility, he wires some devices on Snorlax and Snorlax runs on the training line and when it is about to jump across an obstacle, Daniel jumps to get Snorlax jump safely and quickly.
While impressive, Ash tells Daniel that he and Pikachu do not need technology to be bonded or to train. Daniel responds that he is bonded with Snorlax via science, making Ash a bit angry. Ash challenges him to a battle to prove his words. Daniel refuses, but offers him to compete in the Pokéathlon; a series of challenges where a trainer and his/her Pokémon compete, which is held in Camellia Town. Brock and Ash know of this as they traveled in Johto when it was held. They look upon the poster to see what challenges are present, so Ash is tempted to enter. Daniel does not believe that a non-scientist could defeat him.
As they come to the registration booth, Dawn tells Ash she won't be participating, as she needs to focus on the Contest. Daniel does not believe he would be defeated by feelings, but Ash notices Snorlax seems a bit sad from all the training it received. Daniel checks this via the computer and realizes Ash was right, though baffled that Ash did not use computers to know. James and Meowth approach and advise Daniel his Snorlax could use a massage. Though Daniel is a bit skeptical, he leaves the tent, which makes Team Rocket pleased they got themselves a new Pokémon for the boss. James and Meowth advise Ash as well his Pikachu could use a massage. They take Pikachu (who seems that he needs massage) and go in the tent.
The Pokéathlon starts. The first event is Disk Catch, where the trainer jumps on a board so his/her Pokémon is launched in the air to get the disk. The disks are launched, the Pokémon jump and push the disks near the trainers. When the event ends, Ash and Daniel got an equal amount of disks and win. However, Brock and Dawn do not see Ash; he and Daniel went to get their Pokémon. At the tent, they see Team Rocket are getting away. However, Daniel's Snorlax is too heavy for the balloon to go off.
Jessie sends Yanmega, who uses Steel Wing to cut the rope. Snorlax is freed, so they take off with Pikachu in their possession. Ash sends Staraptor to free Pikachu, but gets poked and defeated by the robotic arms. While pleased, they blast off when Snorlax crashes the balloon by jumping from the trampoline. Ash runs to get Pikachu before he falls, but Snorlax comes and Pikachu lands on it. Ash thanks Daniel, though Daniel responds he wants to beat him using science. Suddenly, they get a call they need to report in the arena, so they run inside. They come in time for Hurl Dash. When they come to their places, they receive headgear (which works on the principle Daniel used to train with Snorlax in his facility); simply put, the trainer needs to react to jump so that their Pokémon can react in time, as they can only get the trainer's transmission when to jump.
The trainers do well; in the lead are Ash's Pikachu and Daniel's Snorlax. Before the finish line, Snorlax and Pikachu charge towards the end. It is a close call, but upon viewing the slow-motion video, Snorlax won by a belly. Ash congratulates Daniel and thinks he should train somewhen like he did. Daniel admits he paid attention what Ash said and felt Snorlax's emotions. They shake hands, which reminds Dawn of her next Contest in Daybreak Town.
- The Pokémon on the Pokéathlon poster were all introduced in Generation II, referencing the fact that in the anime, the first Pokéathlon was held in Johto, a reference to Pokémon HeartGold and SoulSilver.
- Possibly, Meowth also references the said games by mentioning "heart and soul" in the motto.
- The same device used to torture Kaiser in the episode The Legend of Dratini appears in this episode.
- Meowth breaks the fourth wall by saying "this is a reality show".
- Ash and Brock mention events that happened off screen, namely that they knew of the Pokéathlon when traveling through Johto, the episodes of which aired before the Pokéathlon even existed.
Right in the beginning, Dawn is shown in the middle of Ash and Brock, though Ash is shown in the middle in the next scene.