Ash, Brock and Misty get sidetracked on their way to Viridian City when all of their belongings mysteriously disappear. While searching for their missing things, the group find themselves mixed up in a close encounter that's really out of this world!
Jigglypuffsings its song in the woods, putting a nearby wildPidgey and Caterpie to sleep. After scribbling on their faces, a teapot drops on its head. It looks up to notice a UFO overhead just before it crash-lands nearby. Jigglypuff walks over to it to see some Clefairy get out.
The next day, Ash, Misty, Brock, Pikachu, and Togepi are eating ice cream when a Clefairy walks up to them. They chase Clefairy, but while they are gone, more Clefairy steal their ice cream and backpacks. When Ash and his friends go to Officer Jenny, they discover that many other people have also been robbed. As Brock questions why the robbers chose such obscure items, a man named Oswald enters and believes the string of thefts are the work of aliens. Officer Jenny reveals that objects began disappearing three nights ago.
While searching for the aliens, they see a UFO land in front of them. Two silver aliens come out and abduct Pikachu, but they are really Jessie and James in disguise. They put Pikachu in a glass container that absorbs electricity into a lightbulb. The UFO is really being operated by Meowth, using a crane. Ash summons his Pidgeotto, which brings down the UFO. Before the battle with Team Rocket can continue, Clefairy appears, and Oswald's scanner says that it is an alien. It says the same thing about Jigglypuff when it shows up. When the scanner says Misty is an alien, she knocks it out of his hand, breaking Oswald's comic book-ordered scanner.
A Clefairy grabs Pikachu and runs off with him, still trapped in his shockproof container. Ash, Misty, Brock, Oswald, Togepi, and Jigglypuff chase after it and go down a manhole cover that leads to an underground cave. There they see the Clefairy have been using their stolen items to build a spaceship attached to a rocket, and they plan to use Pikachu's electricity to power it and make it blast off. Ash, Misty, Oswald, Togepi, and Jigglypuff enter while Brock goes back to tell Officer Jenny. Team Rocket also enters, intending to steal Pikachu and all the Clefairy.
Inside the ship, Jigglypuff defeats all the Clefairy with a series of Pound attacks, and later battles the leader, who is in the cockpit. Oswald makes his way to the cockpit and tries to pull a lever, but it breaks off. It turns out to be Jigglypuff's marker microphone, which Jigglypuff takes and then sings its song, putting everyone inside the ship to sleep. The ship is timed to take off, and does. The stolen items are all lost during the takeoff, and are returned to their rightful owners. The rocket, with Team Rocket still aboard, detaches from the ship and falls. Ash finds Pikachu, whose Electric attacks are too powerful for his prison, shattering the glass. Ash, Misty, Pikachu, and Togepi escape from the ship, using Ash's Bulbasaur's Vine Whip to grab onto a skyscraper as the spacecraft continues its ascent.
Later, the Clefairy's UFO returns and lands in a small village to take more items from locals for their next escape attempt. Oswald gets out, inside a cardboard box for a helmet, as he believes himself to be on the Clefairy's home planet.
Ash and his friends continue their Pokémon journey, unaware that Jigglypuff is following them.
The box for the VHS release of this episode has Oswald's name as "Orville".
When the gang falls out of the rocket ship on to the skyscraper, they don't have Brock's backpack, but later, he is seen wearing it.
After Oswald identifies Jigglypuff as an alien, his scanner continues to beep, but the lights are no longer flashing.
After Meowth slides down the rope, the lines on his coin are missing. They reappear in the next cut.
When Ash and his friends are chasing after Clefairy, Ash is right behind Jigglypuff. Jigglypuff disappears as they enter the alley, but appears again in the next scene.
The timer in the launch cavern marks the minutes in yellow and the seconds in red. However, when the timer is shown right before the countdown ends, the colors are reversed: the minutes in red and the seconds in yellow.
In the dub, Misty mentions she will use the ice cream she is holding to bait Clefairy. When she fails, Ash quips that it might only like chocolate ice cream. In the original, she doesn't mention the ice cream at all and Ash just mentions she'll have another chance to catch Clefairy later.
In the dub, when the Clefairy spaceship takes off and various items fall off of it, a chef catches his kettle and talks about cooking chicken. In the original, he instead mentions the lack of his pot has been bad for business.
In the dub, Team Rocket, disguised as aliens, mutter something that is heard as "nomékop", which is the word "Pokémon" said backwards. In the original, they just make stock alien sounds.
The "light Bulbasaur" pun was originally James stating that it's important to conserve electricity.
In the dub, Oswald's scanner was ordered from a comic book he lost and self-assembled. In the original, it was "the fruit of [his] sweat, tears and 2800 yen development fee".
The "are you thinking what I'm thinking" exchange between Jessie and James was originally them mentioning how Team Rocket was going to board a rocket for the first time. Also, Meowth mentions "Cape Canasta" in the dub, a pun on Cape Canaveral, Florida, and the card game Canasta, while in the original version, he just mentions that it has gotten noisy.
Ash's analogy of Pikachu's electricity being like the excess air that pops a balloon was added in the dub; in the original he just repeats Misty's theory of Pikachu's electricity being too powerful.