Whiscash and Ash (対決！巨大ナマズンと釣り名人！！ Showdown! The Giant Whiscash and the Fishing Expert!!) is the 35th episode of Pokémon: Advanced Challenge.
While resting by a lake with his friends, Ash polishes his Badge Case and remembers all the Gym Battles he's won so far. Suddenly, a wild Whiscash jumps out and eats the case. Ash dives in to go after it to get his badges back, but nearly drowns. He is saved by a Fishing Master named Sullivan who has spent years trying to catch the giant Whiscash. Determined to retrieve the badges, Ash and the others start fishing. Meanwhile, Team Rocket are also trying to get a hold of the same Whiscash.
Brock made the lunch and as May and Max set the table, Ash gazes at his five Hoenn badges. He is ready to get three more for the Hoenn League. The Badge Case reflects sunlight and is targeted by a Pokémon in a lake. Max asks him to bring some water, but while Ash goes, he stumbles upon a can. Ash loses his Badge Case, which flies off and is devoured by a huge Water Pokémon from the lake. The Pokémon, Whiscash, dives into the water. Ash demands his case back and Whiscash shows the case on its tongue, but taunts him by taking the case back. Ash is angry and sends Corphish to use Crabhammer, but Corphish faints from Whiscash's Water Pulse. Whiscash goes back to water, so Ash has no choice to get in the water. Whiscash goes among some lake weed and Ash follows, but soon gets tied by the weed. Ash struggles to free himself, but runs out of air.
He sees Pikachu and grabs him, but soon gets on a boat with a man, who saved him. While Ash sneezes, the fisherman is amused when Ash wanted to catch Nero, the Whiscash, with his own hands. The fisherman tells Nero, who claimed the lake as its own for a 100 years, must have gotten the case when it sparkled by the sunlight. Ash gets upset for losing his badges, but the man, who introduces himself as "the great Sullivan" and "the fishing god", promises he will get the badges back. Max wonders if Sullivan calls himself the fishing god, why didn't he catch the Whiscash in 50 years. This makes Sullivan depressed, so May pounds Max for hurting his feelings. Sullivan leaves them, but he comes back when the heroes convince him they need him. Sullivan gives Ash some rods, but does not give them to the others, claiming they are amateurs. When Brock, Max and May mention he's the fishing god, Sullivan gives them the other rods. The heroes choose the fishing lures: Ash, a Pikachu, Brock, a Lotad, May, a Psyduck, Max, a Kecleon and Sullivan, a Butterfree lure. Sullivan admits he made a plan to get Nero.
Team Rocket observe the situation. Meowth doubts that they'll get a Whiscash, but his doubt is soon removed when he sees the giant one, which soaks them all. Meowth has an idea - they'll give it to their boss. The heroes catch nothing, while Sullivan caught a Carvanha, Magikarp and a Remoraid, but frees them back. The heroes arrives to Sullivan to give them advice, but he refuses. Upon being called a fishing legend, Sullivan is flattered and shares some advice. He claims one should never cast a lure where there are no Water Pokémon. Max claims that it is obvious, depressing Sullivan, who gets cheerful once Ash claims he is a legend. He shows them some lily-pads, stones, logs and reeds; places where they could capture Water Pokémon. Sullivan throws the lure between the trees. Ash goes to throw on the same spot, but he fails, so Sullivan says that he should practice before aiming correctly. Max throws his lure to the spot he wanted, amazing everyone. Sullivan becomes sad once more, since Max managed to succeed in one try. Max fishes a Whiscash, but a smaller one than Nero. Nero appears immediately after, showing the badge case and diving back in the lake.
Team Rocket is also fishing, but with no result. James is frustrated when he borrowed some bottle caps as a lure. Suddenly, Jessie is pulled by her hair into the water. She stands up and sees a Feebas attacked her, so she gets it off her hair. Ash and May did not get any result either, so Sullivan advises them to move to a different spot. Jessie is attacked again by a Feebas, so she gets it off again. Meowth proposes to use Jessie's hair as bait for Whiscash, but she does not approve of the plan. James spots the heroes fishing, so they plan to steal Whiscash after they capture it. Just then, Jessie falls in the water, due to Feebas grabbing her hair again. Ash remembers his badges and the people he battled to get them, so he promises to get them back. Sullivan concentrates, and throws his lure, knowing that Nero is nearby. Sullivan fishes out the Pokémon, but it is a Magikarp.
When Ash casts his rod, he gets something, so Sullivan says he should pull in the opposite direction. The Pokémon is Nero, but Nero pulls the boat, throwing Ash off balance. Ash sends Corphish and orders it to use Crab-hammer on him. Corphish thinks for a while, but does it, so Ash is sent to the rocks. Ash pulls Nero, throwing it on the shore. Ash sends Grovyle, who uses Pound, hurting Nero badly. Ash demands his Badge Case, but Nero taunts Ash. Just then, Team Rocket captures Nero and fly off using rocket jets, so the heroes sail off on the boat. Brock sends Lombre and Mudkip, who use Water Gun to speed the boat up. Grovyle uses Bullet Seed, blowing up the balloon. The heroes arrive while James sends Cacnea, who uses Pin Missile. Grovyle uses Bullet Seed, overpowering and damaging Cacnea. Jessie sends Seviper, who uses Poison Tail, but Pikachu counterattacks with Iron Tail. Meowth is about to capture Pikachu, but Whiscash frees itself by jumping and shaking the ground by using Earthquake. Pikachu uses Thunder, blasting Team Rocket away.
Whiscash coughs, releasing the Badge Case, which Ash gets back. Nero is about to retreat, but Sullivan wants to battle it, sending his Flaaffy, Hannah, who uses Dynamic Punch, hurting Nero. Nero uses Water Gun, but Hannah dodges and attacks with Iron Tail. Hannah attacks Nero with Thunder Shock, but Nero is unhurt, due to it being a Ground-type Pokémon. Brock wonders about Sullivan having a plan from before, so he pulls out a Master Ball. Sullivan claims he worked 50 years to get one. Sullivan throws the Master Ball, but Nero devours the Ball, much to everyone's shock, and goes back into the lake. Regardless, Sullivan promises to hunt after Nero, making the heroes see that is why Sullivan is a legend. During the sunset, Ash is glad he got his badges back, while Sullivan wishes him luck in his next Gym Battle. He also makes it clear they can stop by to do some fishing. The heroes promise that and leave Sullivan.
- Featured Pokémon: Vigoroth, Slakoth, Machop, Zangoose.
- In the beginning of the episode, a classic Pokémon identification can be seen. In this case, it is a Krabby.
- This is the first and, so far, only time where the Master Ball has been used in the anime.
- Whiscash swallows Sullivan's Master Ball, and is not captured. However, in Berry, Berry Interesting, a wild Munchlax swallows a Poké Ball and is captured from the inside out.
- Ironically, Master Ball should capture Whiscash, no matter what.
- This is the second time the main characters are seen fishing in Hoenn. Oddly, Sullivan has to teach Ash and company to fish, even though Ash and Brock have fished several times before and all present protagonists fished in Gone Corphishin'.
- This would be the last time the move Earthquake was used in the anime. The move itself would later cause an episode to be banned because of a real earthquake. Earthquake has not been used or seen since.
- The Poké Ball outline on Ash's Badge case is changed to a rectangle in the dub once again. This was a Kids' WB! exclusive edit as all the international airings and releases as well as the official English site did not include this edit.