An experiment pod ends up in a box of sugar, which is bought by the Pelekais. Pleakley unknowingly adds the pod to his cereal and shallows it as begins to activate. Its activation alerts Gantu, so he suits up to capture the experiment. Meanwhile, while Nani and David are getting ready to go wave riding, Lilo and Stitch are playing with the water scooters when they accidentally break one. Lilo wants to go wave riding as well, only to be told she is not old enough.
When they arrive home, they found Pleakley lying on the couch feeling sick. He is covered in purple pimples, has a swollen eye, his feet stink and is burping uncontrollably. Lilo and Stitch try to help curing him, but he runs away to the clinic after Stitch tries to perform surgery on him with a chainsaw. Lilo and Stitch tell Jumba about Pleakley's symptoms, who identifies this to be the work of Experiment 222: designed to act as a virus and infect popular planetary leaders, giving them purple pimples, smelly feet, swollen eyes, and uncontrollable burping.
At the clinic, Gantu is looking for Pleakey, who has just arrived. He tries to capture him, but he runs. Later, Lilo and Stitch show up in time to save him and tell him about the experiment infecting his body. After escaping Gantu and returning home, Jumba shrinks Lilo and Stitch, along with the X-Buggy, to microscopic size and injects them into Pleakley's body so they can search and capture Experiment 222. Once inside, Lilo and Stitch find themselves travelling through Pleakley's blood. They soon spot 222, and chase after him. However, they fall under attack by one of Pleakley's antibodies. Using some wave riding maneuvers, Lilo manages to shake of the pursuing antibodies. However, they end up passing through Pleakley's hearts. Meanwhile, Gantu shows up and takes Pleakley. Jumba tries to stop him, but Gantu easily overpowers him. He even breaks Jumba's Computer, losing contact with Lilo and Stitch.
Gantu takes Pleakley to his ship and prepares him for molecular transport to Dr. Hämsterviel. Meanwhile, unaware of what is happening, Lilo and Stitch find themselves inside Pleakley's stomach and spot 222. The chase is on once again. They chase him through lung trees and make their way to the eyeball. Stitch deploys the capture cannon and tries to capture 222. He misses and the grapple ends up grabbing the optic disc, which Pleakley reacts to in pain. Lilo and Stitch try the grapple again, but this time 222 catches it and rips of the capture cannon. At the same time, Lilo and Stitch realise that Pleakley has been captured by Gantu and is about to be transported to Hämsterviel. So, they head for Pleakley's brain, where Stitch wires himself to Pleakley's nerves. Connected to his brain, Stitch controls Pleakley's body, helping him escape containment and tries to battle Gantu. Just then, Jumba shows up and shrinks Gantu. Then he turns to Pleakley and calls out to Lilo and Stitch that they need to leave his body immediate. He had been trying to tell them that the shrinking process only lasts for an hour and it was about to wear off. If they start to shrink while still inside Pleakley's body he will explode.
Lilo and Stitch hurry to the nearest exit, which is the ear. 222 is also heading in the same direction, so they pursue him. They make one last effort to capture 222. He ends up getting stuck in the earwax, giving Lilo and Stitch the chance to capture him. Suddenly, they start growing back to normal size and quickly hurry to the mouth. Pleakley burps them out just as they grow back to full size. With Experiment 222 removed from his body, Pleakley returns to normal.
Afterwards, Lilo has come to learn that being little is not such a bad thing. As for Experiment 222, Lilo planted him inside Gantu, who falls ill with the same symptoms Pleakley had. Now he is miserable with itchy pimples and uncontrollable burping, despite the fact he wanted to capture the experiment.
- Moral: You are never too small or too big to do great things.
- This is the first Season 1 episode in production order.
- This episode is based on the 1966 sci-fi film, Fantastic Voyage.
- Stitch attempts to destroy Nani's toaster after it popped toast in his face, a callback to the first film.
- We learn that Stitch has the ability to milk a cow when he fetched a bucket of milk for Pleakley's cereal.
- Since raw milk from a cow's udder usually contains harmful microorganisms, Pleakley might have also gotten sick from consuming such milk.
- Gantu revealed that he hates cherry lollipops after tasting one.
- This is one of three episodes where Gantu gets sick and is revealed to like chicken soup sandwiches, the other two being "Slushy" and "Slick".