Dig Those Diglett! is the 31st episode of the Indigo League season.
Ash, Brock, Misty are lost in the mountains. They hear an explosion in the distance and they run to where they heard the explosion. Elsewhere, Team Rocket tries to enjoy a lunch break only to have their lunch destroyed by an earthquake. Angry about this Team Rocket decides to go after the culprits responsible with Meowth right behind them.
Later, Ash and his friends see several semi trucks in a pile up. Pikachu then hears a sound coming from the ground and a Diglett pops up. Then it pops right back down into the ground. A construction worker tells Ash and his friends that they were building a dam in the area, but a group of Diglett are destroying the construction and the project has been forced to stop. Misty thought they were cute but the director doesn't share her viewpoint.
The worker tells them that the person who gets the diglett to leave will get a big reward. Gary appears along with four buses full of trainers and says he will solve the problem. As usual he insults Ash, and after seeing his cheerleaders, Brock wants their phone numbers but the director tells them to get to work. Team Rocket plans to steal the trainers Pokémon and the Diglett. Then the Director explains the situation and Team Rocket wants in and tries to come up with a plan to steal the Pokémon but James realizes that they won't have much of a chance with Ekans and Koffing. Then Meowth says they'll find a way.
After a brief explanation as to the enemy, and some facts about Diglett from Gary, The Diglett arrive. He tries to send out one of his Pokémon, but his Pokémon refuses to come out of its Poké Ball. Diglett returns it to Gary with his saying that wasn't supposed to happen. He tries with another one but the result is the same. Ash tries to send out his Pokémon, but he has the same problem. He asks Pikachu to battle the diglett, but Pikachu refuses. Other trainers who are also there, try to send out their Pokémon to battle the diglett, but every one of their Pokémon refuse to come out of their Poké Balls and they are returned by the Diglett. Ash tries to use Squirtle, but the result is the same.
Back at the construction site, Gary realizes that it's impossible to stop the Diglett and he and all the trainers except Ash and his friends leave. Ash asks Pikachu why he wouldn't battle Diglett. After seeing it as a waste of time, Gary leaves with his entourage, leaving Brock heartbroken again. That night, while Ash and company relax in a hot spring, Pikachu points to one of the Diglett, who had just stuck its head out of the ground, and Ash, Misty and Brock emerge in their swimwear. After getting dressed, Ash and his friends start chasing it and the construction worker tries to whack the Diglett with a mallet.
Jessie and James find out that inorder for their Pokémon to evolve they have to win battles, and when they do, they become entirely different Pokémon. They feel some sentiment for being with Ekans and Koffing for so long they cry. This triggers their evolution process.
Ash and his friends chase the Diglett to a forest. In the forest, many Diglett and Dugtrio are planting plants. Ash and his friends realize that building the dam would make the forest hard to live in and it would destroy the work the Digletts and Dugtrios are doing. That's why all the Pokémon refused to fight the Diglett. The construction director decides to cancel the project.
Team Rocket appears and they are extremely happy because Ekans and Koffing have finally evolved into Arbok and Weezing! Pikachu uses Thunderbolt, which Arbok dodges. Arbok digs underground, followed by Weezing. For a minute, nothing happens and then suddenly Arbok and Weezing come up out of the ground beaten and bruised by the Diglett. They crash into Jessie and James, who crash into the foundation of the dam.
When the construction company learns of what the Diglett and Dugtrio are doing, they agree to stop building the dam. Ash and his friends set off looking again for Fushia City.
- "Ash, uh shouldn't we put some clothes on?"
~Brock after he, Ash and Misty emerge from the water in their swimwear.
- "They know the rest."
Meowth breaking the fourth wall.
- Ash: "Ahhh. Team Rocket? I forgot about them. Sorry guys but we're not in the mood for you right now. Okay?"
Jessie: "Tch tch tch tch tch. But, we're in a good enough mood for everyone."
James: "Yes, and we never even had lunch. But now we have a special treat for you."
Jessie and James prepare by dressing as sushi servers.
Jessie: "A treat with a sensational and exciting new flavor."
Meowth: "For the first time on TV."
Jessie: "We're proud to present..."
James: "...Our new Pokémon."
Jessie: "Our Ekans has evolved into... ARBOK!"
Arbok emerges from its Poké ball.
James: "And Koffing is now... WEEZING!"
Weezing emerges from its Poké ball."
- This is the last episode where Nathan Price voices Meowth before passing the torch on to the late Maddie Blaustein.
- This is also the last episode we see Jessie's Ekans and James' Koffing.
- The construction director tried to get rid of the Diglett by hitting them with a hammer. This is a fashion similar to the game "Whack-a-mole."
- Meowth broke the four wall when Koffing and Ekans are revealed to have evolved.
- When Ash and Co. discover the Digletts' home, Brock wrongfully states that the diglett plow the fields and the Dugtrio plant the trees, when it was actually the other way around.
- The "Who's that Pokémon?" in this episode is Diglett.