Zigzag Zangoose (ザングースＶＳハブネーク！ライバル対決！ Zangoose VS Seviper! Rival Confrontation!) is the 8th episode of Pokémon: Advanced Challenge.
Traveling on the road, the heroes encounter Nicholai, who had caught a Zangoose. While having a battle with Ash, Nicholai notices Zangoose is acting strange. Just then, Team Rocket appears, whose Seviper starts battling Zangoose and injures it. Due to Zangoose being Seviper's natural enemy, Ash decides to help Nicholai in training, to let Zangoose defeat Seviper.
A Pokémon is running past by the heroes. May wonders which Pokémon it is and is told it is a Zangoose. Another one arrives, speaking human language. May is startled by this Zangoose, who is actually Nicholai, dressed as a Zangoose. Nicholai admits challenged the Petalburg Gym leader Norman, May and Max's father. He also told he was their friend, which caused their mother, Caroline, to give him a dinner. While Nicholai didn't win, but he is proud to challenge Norman as the Knickerbocker, though May and Max doubt their father would wear shorts, even during the battle. Nicholai pats them on the back, claiming all great trainers would wear one. Since Nicholai came here to train so he can have a rematch with Norman, Ash challenges Nicholai to another battle, to which Nicholai agrees to.
Nicholai puts the Marshtomp costume and sends his Marshtomp, which evolved from Mudkip, while Ash sends Treecko. Marshtomp starts off by using Water Gun, but Treecko evades and uses Quick Attack. However, Marshtomp does not stop using Water Gun, managing to thwart Treecko's attack. Marshtomp uses Mud Shot, hitting Treecko. Marshtomp uses Iron Tail, but the attack is stopped due to Treecko's Bullet Seed. Treecko attacks using Pound, defeating Marshtomp. Team Rocket, who is watching the battle, identified Nicholai dressed in Marshtomp costume. Still, they want to capture Pikachu, so Jessie sends her Seviper, ordering it that when Ash looks in other direction, it will grab Pikachu. Nicholai changes into his Zangoose costume and sends Zangoose. Nicholai orders Zangoose to use Swords Dance, but Zangoose does not obey the order and goes in other direction, sensing something. Zangoose goes in the bushes, ambushing Team Rocket, who reveals themselves.
Zangoose and Seviper, however, want a battle. Nicholai sees Zangoose knew there was a Seviper around. Max tells May Zangoose and Seviper are natural enemies, while Brock points out when one senses another, they have an urge to battle. Seviper and Zangoose clash; Meowth orders Seviper to focus on grabbing Pikachu, but in response, Seviper uses its tail to hit Meowth, making him bash into Jessie and James and causing them to fall in a river. Seviper wraps Zangoose, but Zangoose bites its body and they both fall into a river. Even in the river, Seviper uses Poison Tail, hitting Zangoose. Ash sends Corphish, who uses Bubble Beam on Seviper. Seviper is hit, so Corphish carries Zangoose to the shore. Seeing Zangoose has taken a lot of damage, Brock advises going back to the camp to let Zangoose rest. Being there, Brock made a herbal soup for Nicholai to give to Zangoose, to let it rest. May and Max sense Zangoose is still angry and wants to battle Seviper.
Team Rocket, however, has been washed on shore, miserable for their failed plan. Seviper comes to them, so James scolds it for messing up, but Seviper intimidates him, causing James to apologize. Meowth translates Seviper wants to battle Zangoose some more. Jessie feels the same way, she wants to tear Cassidy into pieces, once and for all. Jessie decides to help Seviper to defeat Zangoose. Nicholai wants to train with Zangoose before they battle Seviper. So, Nicholai and Ash dress as Zangoose and Seviper. Ash uses the costume's tail to attack Nicholai. Nicholai is knocked out, but stands up, as Ash points out Seviper can use its tail quite fast. Ash uses the tail once more and Nicholai evades, but Ash bites Nicholai, since Zangoose puts itself at close combat risk. Nicholai thinks there is no way to beat Seviper, but Ash wants him to think on how to defeat it. May and Max are skeptical that it will do any good to Zangoose, but Brock states the better Nicholai thinks like a Zangoose, the closer he will be to his Zangoose.
Skitty goes out of its Poké Ball and plays with Ash, who runs off. May jumps to catch Skitty, but fails. Suddenly, they hear Seviper approaching; Zangoose stands up and goes after it. Brock fears Zangoose is done for, since it has not fully recovered from its last battle. Jessie and Seviper try to get Zangoose to come to them. James claims this is a waste of time, but Meowth reminds him arguing with Jessie is actually a waste of time, since this could be their opportunity to catch Pikachu. Zangoose finally arrives, as do the heroes and Nicholai, the latter promising to defeat Jessie. Seviper attacks Zangoose, who dodges the attack. The heroes support Nicholai, but a mechanical arm, used by Meowth, grabs Pikachu. The heroes go after James and Meowth, but they stop as Zangoose and Seviper have a battle. Pikachu uses Thunder, but the cage is electric proof. James and Jessie ask Jessie to come with them, but she is staying with Seviper until Zangoose is defeated.
James and Meowth go away, leaving Jessie behind, while the heroes follow them. Seeing their enemies coming, James brings Cacnea, who hugs the former, uses Pin Missile to stop everyone. Meowth and James say their motto, with the former replacing Jessie, who is glad to have replaced her. Ash goes after Pikachu, but is blown away by Cacnea's Sandstorm. However, Ash is blown onto James and Meowth, causing them to drop Pikachu's cage, which goes flying off. Zangoose and Seviper continue their intense fight. Seviper uses Bite, but Zangoose dodges. Seviper uses Poison Tail, but it misses. Nicholai is happy that the training with Ash paid off, but Zangoose is too tired. Seviper is about to finish Zangoose, but Pikachu falls into the middle of the battlefield. The heroes, James, Meowth and Wobbuffet show up. They fall on the ground, fighting to get Pikachu. In the end, Jessie's Wobbuffet gets the cage and goes away, so everyone goes after him. Nicholai sees them moving in a zigzag pattern and compares it when Ash was chased by Skitty, so he comes up with a plan. Jessie yells, causing everyone to stand still, though Ash snatches Pikachu from Wobbuffet's hands. James and Meowth claim they are the cheaters, but Ash reminds them they stole Pikachu in the first place.
Seviper attacks, so Zangoose retaliates. However, Seviper misses and goes after Zangoose. Brock notices that Zangoose is moving in zigzag pattern, doubting Seviper will win this one. Jessie orders Seviper to use Bite and Poison Tail, but Zangoose jumps, dodging the attacks. Zangoose uses Crush Claw, defeating Seviper. Despite the defeat, Jessie praises Seviper for the courage, since it battled extraordinarily. Meowth interrupts, wanting to get Pikachu. Cacnea is brought out again and uses Pin Missile on everyone. Striking back, Pikachu uses Thunder, blasting Team Rocket off. Nicholai praises Zangoose and thanks Ash for the training. Later, Nicholai resumes his battle with Ash, sending his Zigzagoon, so Ash sends Pikachu to battle. As Zigzagoon and Pikachu battle, May sees Nicholai could become a really good trainer, while Max claims everyone would even wear blue shorts.