Hooked on Onix (Japanese: イワークの王国！！The Kingdom of Iwark!!) is the 137th episode of the Advanced Generation series, and the 411th episode of the Pokémon anime. It was first broadcast in Japan on August 4, 2005 and in the United States on May 6, 2006.
Ash's Battle Factory victory has him eager to reach the next Battle Frontier stop right away, but even he has to stop for food and water. Munchlax takes care of the Pokémon food by eating it all, which sets off a squabble that disturbs the local Geodude. The Geodude chase Ash and May's Pokémon, and some of them are separated in the commotion. Ash and May have to find their missing Pokémon!
An Onix leads the Rock-type Pokémon that live in the area, and they're none too happy about the intruders. Team Rocket sees this and convinces Onix that Ash and his friends are up to no good. Phanpy and Squirtle reunite with Pikachu, Corphish, and then Munchlax, but they're captured by Rock Pokémon working with Team Rocket. Elsewhere, Brock is captured as well!
Ash finds Onix and Team Rocket, but now all his friends and their Pokémon have been snagged! Ash tries to tell Onix that he's not a villain, and Onix decides that they'll battle. If Ash wins, his friends go free. If Ash loses... well, he'd better win! Ash choses Grovyle, who has a type advantage against Onix, and wins the round.
Team Rocket tries plan B: steal all the Pokémon outright. But Ash tells Grovyle to defend Onix against their attack, and it's clear now who the good guys are. May and the others are freed, and together everyone protects the wild Pokémon from Team Rocket. Once the villains are sent flying, Onix makes amends by giving our heroes an escorted ride out of its valley.
Ash and his friends head towards the Battle Arena after he earns the Knowledge Symbol from Noland. His friends are so exhausted that they decide to take a break. After walking some more, Ash collapses to the ground in exhaustion and his friends tell him that they should have taken a break already. Ash says that he needs water, but the canteen is empty. Brock suggests that they go search for water and that Max should look after the Pokémon while he is gone. While searching for water, Ash falls down the steep hill out of exhaustion and his friends say that they should have left him behind instead of Max. Mudkip shows them where the water is. Meanwhile, Max is feeding the other Pokémon and decides that he should be able to take a nap. Munchlax eats everyone's Pokémon food which makes everyone mad and Squirtle cry. Corphish tries to attack Munchlax with Bubble Beam, but it misses and hits Squirtle. Squirtle uses Bubble which hits Corphish. Pikachu tries to wake Max up but is not able to. Squirtle and Corphish continue to battle each other as their attacks disturb a group of Geodude.
The angry Geodude surround the other Pokémon and get ready to attack them, but Phanpy uses Rollout to escape. The Geodude begin using Rollout to attack everyone as they knock out Corphish, send Munchlax flying, and begin chasing Pikachu and Corphish away from the group. Max rushes over to check what is going on and notices that Munchlax, Corphish, and Pikachu are gone. Ash and his friends return as Max tells them what happened and that some of the Pokémon are missing. They decide that they should look for the Pokémon with Mudkip coming along while Brock stays back to look after the remaining Pokémon just in case the others return.
Meanwhile, the angry Geodude go to their clan, consisting of multiple Graveler, Golem, and a single Onix and tell them what happened with the other Pokémon. Meowth of Team Rocket calls Onix the king of the Rock-type Pokémon and decide that they should try to convince Onix that Ash and his friends are evil enemies. Team Rocket translates that the Geodude are telling Onix that several of Pokémon owned by Ash and his friends were causing them major problems. Jessie starts off by complimenting Onix and then tells it that Ash and his friends are evil Pokémon Trainers run by the leader Ash. As Jessie was telling Onix about Ash, it was picturing how evil Ash was with a beard. She tells Onix that they are planning to steal all of the Rock Pokémon, so Team Rocket wants them to go after all of them.
As Ash and Max are searching for the Pokémon, Max gets very worried about them, thinking that he would be in trouble if the Geodude really injured the Pokémon. Pikachu and Corphish are looking for everyone, but are walking a different direction than Ash and Max are. In a flower field, Squirtle is smelling flowers and admiring a large one when a Beedrill pops out and begins to attack. Phanpy uses Hidden Power to send Beedrill away. Squirtle continues to pick flowers until a swarm of Beedrill chase after them. Phanpy puts Squirtle on its back and runs away in fear. To their surprise, they run into Pikachu and Corphish, but keep running away. Pikachu and Corphish see the swarm of Beedrill coming and use Thunderbolt and Bubble Beam to send them away.
Brock starts to get frustrated with everyone taking so long and thinks he should go look for them. A group of Geodude appear and surround him before a locked cage lands on him. Pikachu, Corphish, Squirtle, and Phanpy continue searching for everyone and find Munchlax eating apples in a tree. Geodude and Golem appear and use Rollout to chase them. The Pokémon jump on a log that is in a river and use it to avoid the Rock Pokémon since they hate water. They hit a rock and fall into the water and down the waterfall. Back on land, they end up surrounded by Graveler and Golem and are trapped in a cage as well. Pikachu uses Thunderbolt and Corphish uses Bubble Beam to try to break the cage, but they fail.
Up on the cliff, Brock and the other Pokémon are stuck in cages while Brock tries to figure out what is really going on. At the bottom of the cliff, Mudkip lets Ash and his friends know that all of the Pokémon are at the top. Ash climbs the cliff as a cage falls on top of his friends. Team Rocket recites their motto and everyone realizes that the Rock Pokémon for some reason are working for Team Rocket. Meowth says that they've waited a long time to capture Pikachu and finally have. Team Rocket thanks Onix for capturing Max, May, Brock, and the Pokémon and ask that they keep them from ever harming Pokémon again. They say they are going to take the Pokémon with them and away from Ash and his friends. Ash steps in to speak to Onix to try to make it understand that he would never hurt the Rock Pokémon and that Team Rocket are the ones trying to steal all of the Pokémon. Onix doesn't know who to believe and Meowth translates that Ash must defeat it in a battle and prove that he has to be telling the truth. Ash brings out Grovyle to battle Onix. Brock warns that Ash must be careful since Onix is at a high level, despite being at a great disadvantage against a Grass-type.
Onix uses Slam, but Grovyle dodges and uses Quick Attack, hurting itself against Onix's hard body. Onix uses Headbutt to knock Grovyle into the wall. Grovyle lands a hit with Bullet Seed. Onix tries to Bind Grovyle but Grovyle avoids it. Grovyle uses Bullet Seed again but this time at Onix's head, causing major damage. Grovyle then finishes it off with Leaf Blade. Team Rocket panics and thinks that they should just grab Pikachu and run for it. Meowth suggests his plan to take the powerful Onix with them as well. Team Rocket reappears inside of a large mecha which throws a massive boulder at Onix. Grovyle uses Leaf Blade to destroy the rock before it can harm the weakened Pokémon. Onix commands the other Rock Pokémon to break the cages and to protect Ash and his friends from harm. Team Rocket blasts the Rock Pokémon with water from the mecha's water cannons, knocking them all out. They use the robot's arms to grab Pikachu and Onix while trying to make their getaway, but the Rock Pokémon are holding them back. Mudkip uses Water Gun, Corphish uses Bubble Beam, and Squirtle uses Bubble to break the arms of the robot. Pikachu uses Thunderbolt and Onix uses Iron Tail to send Team Rocket blasting off. As thanks for helping the Rock Pokémon fight Team Rocket and perhaps an apology as well, Onix gives Ash and his friends a ride on its back as it transports them to the Battle Arena.
This episode marks one of the rare occasions in which a member of Team Rocket refers to one of the main protagonists by name. In this occasion, Meowth calls Ash by his name.
When this episode first aired in the U.S., the title card spelled Onix as Onyx. This mistake was corrected by the time the episode first aired in the UK, and remained corrected for reruns, streaming releases, and the DVD release.
In a closeup of Phanpy being scared by the swarm of Beedrill, its left eye is unchanged while its right eye is white.