Ash, Misty, and Tracey are riding Lapras toward their next adventure. They see a small cluster of islands, and Tracey tells them that they're known as the seven Grapefruit Islands. They are covered with Grapefruit groves that should be ripe by now. They head over, with Jigglypuff soon behind.
They reach one of the islands, and rave at the size of the huge fruits. Ash reaches up and picks one, and young woman runs up to them with a stick. She accuses them of stealing, and they object, telling her that they didn't know people actually tended to the trees. She apologizes and tells them that someone has been stealing a lot of fruit. She goes on to tell Ash and his friends everything that they do to make the grapefruit grow as big as they do. A man runs up and tells the woman (Ruby) that more fruit has been stolen. They all rush over to the scene.
Upon arrival, they are stunned at what they see. Not only is the grapefruit in this section gone, but the branches off the trees are missing too. The worker calls them over to a different part, and they see a Snorlax sitting and eating branches and branches of grapefruit. Several workers rush over and try to move the huge Pokémon, but to no avail. Ruby tells everyone to start picking the grapefruit before Snorlax gets at them, and Ash suggests that they use their Pokémon. Bulbasaur and Staryu are sent out, and soon they have a huge pile of fruit sitting on the ground.
Unfortunately for them, Snorlax rushes over, plops down, and starts to scarf down the fruit. Tracey suggests that they weaken Snorlax and catch it, and Bulbasaur attacks. It doesn't work, however, and Snorlax uses Body Slam against it, flattening it.
Snorlax finishes that pile of grapefruit, gets up, and walks over to a patch of fresh fruit. It repeats this every so often, eating and eating, until the entire island is devoid of grapefruit. Misty says that now it won't be able to eat anymore, but this relief is put down when it stands up once again and dives into the water. It starts to swim over to another island. Ruby jumps into a motorboat to tell the other islands to start picking the fruit, and Ash and his friends follow Snorlax on Lapras.
Meanwhile, on the island that Snorlax is heading, Team Rocket is gathering a bunch of grapefruit. Meowth tries to slash open one with his claws, but fails. James suggests that the grapefruit are actually grown to make candied grapefruit peels. Jessie tells them that they should sell the fruits and they take them to the Magikarp sub. Before they can get in, however, Snorlax reaches the shore and starts to eat the fruit the Rockets had gathered. Ash and his friends show up and tell Team Rocket to go away, and Meowth tells Jessie and James that they can get Pikachu and a Snorlax.
A worker on the second island calls Ruby at headquarters. He tells her that Snorlax is eating with the same gusto that he devoured the first island with. Ash and his friends show up, and Ash sends out Squirtle, who uses Skull Bash. It doesn't do much, and Squirtle is flattened like Bulbasaur before. Misty's Staryu gets Headbutted, and Goldeen almost gets eaten. She then tries to use Togepi, but it just sits there.
Team Rocket decides to try, and Jessie sends out Arbok. It gets flattened, and Lickitung's tongue is used as a napkin. James uses Victreebel who, after eating James again, gets flattened as well by Snorlax's Body Slam.
Misty decides to try again, using Psyduck. It sees a Grapefruit that Snorlax missed and eats it whole, only to choke. Ash then decides to use Pikachu, but it's electric attacks have absolutely no effect. By this time, Snorlax has eaten about half the island's grapefruit, according to the worker talking to Ruby. Another worker at the headquarters tells her that she’s needed at the Processing plant and she hurries off.
Ash and his friends resign themselves to the fact that Snorlax is too strong for their Pokémon, and James decides to try out a new tactic: Hypnosis. He waves a pendent in front of Snorlax's face, but only succeeds in putting himself to sleep. This gives Ash and his friends the idea of putting it to sleep, and try massaging it. When that doesn't work, Misty tries to get it to count Snorlaxes. After 102, she falls asleep herself.
Jessie dresses up as Snorlax's mother and tries to persuade it to take a nap. James and Meowth sing a lullaby, but Snorlax gets aggravated and Mega Kicks them into the air and out of the episode. It dawns on Ash and his friends to find Jigglypuff so it can put Snorlax to sleep. They hurry over to the headquarters to find Ruby standing in the middle of all the workers asleep. Ash notes from the marks on the faces that Jigglypuff must not be far away. The computer screen goes off, telling them that Snorlax is swimming towards the third, and biggest, island. They decide to set up a stage for Jigglypuff.
They build a stage with flashing lights and even include a box of multi-colored markers. They admire their work for a moment and Snorlax shows up on the scene. Ruby worries that it'll get at the grapefruit in the warehouses and they start to clap and chant for Jigglypuff. It shows up and starts its song. Ash resists the haunting melody and runs over to Snorlax, who is already swaying to the music. Pikachu uses Thunder, and Ash throws a Pokéball at it. It doesn't shake at all. Ash cheers for a second, then falls asleep.
Jigglypuff realizes that everyone is sleeping, gets peeved, and uses the colored markers to draw all over their faces. Later that afternoon, as the sun sets, Ruby thanks Ash and his friends for their help. She gives them a bag of candied grapefruit peels and they eat a few. A worker approaches and tells Ruby that there are new grapefruit trees growing everywhere Snorlax was. Misty comments that this must mean that something good can always lead to something bad. Ruby agrees, and Ash and his friends ride off.