Ash and his friends continue towards Goldenrod City. Brock reads his guide and informs everyone that the Onix Tunnel, a mountain pass filled with Onix, is close by. Misty is worried about the Onix, but Ash assures her that his Squirtle can handle them, only to remember that Squirtle is now with the Squirtle Squad. Misty replies that her Water Pokémon will do the job. With the sun setting, the group decides to wait until the morning to enter the tunnel. Unknowingly, Jigglypuff walks closely behind them, and Snubbull follows closely behind.
A new morning arrives and Team Rocket walk to the cave's entrance. Meowth considers taking the mountain route instead, but he reluctantly takes the tunnel path with Jessie and James. The cave's eerie silence is broken by a trio of Onix. James calls out his Victreebel. He orders Victreebel to use Razor Leaf, but the Onix don't seem affected by it. They reply by hitting their heads against the cave's walls and using Rock Throw to cause a rockslide. Jessie decides to send out Arbok, but it is quickly Binded by one of the Onix. After that, Jessie tosses Meowth at the Onix, but his Fury Swipes do nothing. The Onix reply by using another Rock Throw. Team Rocket rushes out of the tunnel. They gather their breaths before deciding to steal Misty's Water Pokémon in order to counter the Onix. Wobbuffet pops out of his Poké Ball, but Jessie quickly recalls him.
Meanwhile, Ash and his friends are just beginning their day. Ash sits by the campsite's river to wash his face, while Brock stretches with Pineco and Misty scolds her Psyduck for its habit of putting its hands on its head. Brock asks Pineco if it's ready to have some fun, and Pineco promptly explodes in Brock’s arms. Ash notices a Snubbull walk by, and he instantly notices its red ribbons. Misty says that it's obviously the Snubbull that belongs to Madame Muchmoney. As the group wonder why she has run away from home, Snubbull rushes off. Ash and his friends pursue Snubbull, but soon lose her only to find themselves face-to-face with a familiar Jigglypuff. Before the group can flee, Jigglypuff jumps onto a tree stump and performs a Singing rendition which causes Ash and his friends to fall asleep. Team Rocket, who have disguised themselves as shrubs, and Snubbull, who was about to bite onto Meowth's tail, are also lulled to sleep.
Sometime later, Snubbull wakes up, with her face scribbled by Jigglypuff and with no sign of Team Rocket. She starts sniffing again, arriving at a small pond. When she looks at her reflection, she is shocked to see what happened to her face. Then she turns and sees an angered Jigglypuff is scribbling on a sleeping Pidgey. Snubbull steals Jigglypuff's microphone and runs away with it. Soon Ash, Brock and Misty encounter Jigglypuff again. They attempt to run, but Brock stops them, saying there is something different about it. Then Ash notices it doesn't have its microphone. They decide to help it find the microphone.
Meanwhile, Team Rocket have since cleaned their faces of Jigglypuff's scribbles. With their first plan ruined, Jessie suggests the trio try a pitfall trap. She introduces her teammates to a new invention, a shovel combined with a pogo stick. Snubbull appears with the microphone, while Team Rocket is digging. She sneaks behind Meowth and bites down on his tail. Jessie picks up Snubbull and quickly identifies it as Madam Muchmoney's Snubbull. James thinks it would be a great gift for their boss. Though Jessie is glad to have a cute Pokemon like Snubbull to cuddle, and mentions that she will now become more popular than Misty and her Togepi. Wobbuffet makes another unexpected appearance, much to Jessie's annoyance. Meowth demands that Jessie and James pick either him or Snubbull, but he is shocked that his teammates happily welcome Snubbull to the group. Jessie and James soon leave, and Meowth goes on his separate way. Later, Team Rocket spy from some bushes as Ash's group and Jigglypuff notice several plates of fruit lying on the road ahead. Ash is eager for a bite, but his friends are more skeptical and believe it's a trap. Jigglypuff rushes forward and falls into one of the pitfall traps. Ash sends his Bulbasaur to rescue Jigglypuff out of the hole. It becomes angry, runs toward two more pitfalls with Bulbasaur taking it out of both holes. It puffs up again in anger and runs, while the gang follows it.
Soon after, Snubbull jumps from Jessie's hands and rushes off. Elsewhere, Meowth contemplates returning to Jessie and James, but he quickly changes his mind. In the forest, Ash and his friends search for Jigglypuff's microphone, but Jigglypuff is quickly losing hope of locating its precious item. Now Meowth rests by the entrance to Onix Tunnel and a sad Jigglypuff joins him. The pair begin to console each others feelings and Meowth suggests that he and Jigglypuff should start their own team named the Dream Team. The conversation is shortly interrupted after Snubbull bites Meowth's tail. Jessie and James appear, but they admit they didn't notice Meowth's disappearance and were only looking for Snubbull. Jigglypuff spots its microphone in Snubbull's paw and tries to snatch it back. Just as Jigglypuff and Snubbull begin fighting, and Meowth also gets caught up, Pikachu oversees the commotion and quickly alerts Ash's group. Ash and his friends rush on to the scene and break up the fight.
Team Rocket is glad to see Misty and recites their motto. Meowth tries to say his classic line, but Wobbuffet interrupts. Jessie and James are quite impressed by the new rendition, but Meowth is admittedly concerned about his future in Team Rocket. Jessie sends her Arbok and Misty tries to send one of her Pokémon, but Psyduck pops out instead. Team Rocket cringe at Psyduck’s arrival, though Misty quickly recalls it. She tries again and sends out Poliwag. Poliwag dodges Arbok then hits it with Water Gun. James sends out Victreebel and Ash calls on Chikorita for assistance. James orders Victreebel to use Razor Leaf on Poliwag, but Chikorita’s Vine Whips break the attack. Poliwag Double Slaps Arbok and Chikorita uses Razor Leaf on Victreebel. Chikorita follows up with a Vine Whip, but it is Countered by Wobbuffet. Poliwag powerful Water Gun manages to break Wobbuffet's Counter and throws him, Victreebel and Arbok back into Team Rocket. Pikachu uses Thunderbolt and sends them blasting off. Snubbull runs off to chase Meowth, leaving the microphone behind.
Jigglypuff picks up the microphone and starts singing, putting Ash, Misty and Brock to sleep again then scribbling their faces. As they sleep, Jigglypuff enters the tunnel and encounters the three Onix. It starts singing again, putting them to sleep. Ash's group wake up by sunset and proceed to pass through the Onix Tunnel. They are relieved to see the Onix are fast asleep, and Ash is grateful that Jigglypuff was reunited with its microphone. By nightfall, Team Rocket begin their walk through the Onix Tunnel. Jessie unfortunately trips over, and the sound causes the slumbering Onix to awaken.