Stitch doesn't know how to take care of anything, or things that don't belong to him. He's already got Nani in trouble at the Rental Shack, by breaking the Shake Machine. However, when Richter turns up and is causing earthquakes, will Stitch be able to stop him breaking everything... Even his favourite ball?

A bird has discovered a strange blue ball in her nest. After deciding she doesn't need it, she discards it into the river running below her tree. It turns out it's #520's pod, and it activates. Now the experiment is wreaking havoc over the island with it's huge behind by bouncing and shaking the ground. So, Lilo and Stitch must capture it, but Gantu is on it's trail too.

It's Lilo's birthday, but no one has remembered. So, she decides to give herself her own party. However, during the day, Experiment #303 is activated and wipes Lilo's, Stitch's and Gantu's memory. Lilo and Gantu, who think they are Martha and Lenny go after Stitch, who has returned to his natural destructive programming, and so they think is a criminal.

Stitch has been recently very successful at capturing and repurposing the Experiments, but it's gone to his head. He thinks he's too good for everything and is being a royal pain.

But things are set to change when Pleakley goes into Jumba's ship and sees an experiment pod with the number '627' on it. Jumba has been making a new experiment. Luckily, it's in containment. That is, until they leave the ship and it escapes! Now it's employed by Gantu and Stitch wants to prove he's better than it. But he just gets beaten, and as 627 can't be turned good, Lilo and Stitch are in trouble...

In a trip to the observatory, Lilo and Stitch overhear Cobra telling an astronomer about a huge asteroid heading towards Earth. Lilo and Stitch go around Kauai telling the people to evacuate with them onto their ship. Stitch also warns his cousins. However, only 6 Experiments - Digger, Swirly, Hammerhead, Sparky, Spooky and Kixx - and a surfer from the beach arrive at the ship. So, Stitch comes up with a new idea; Digger will drill a hole to the center of the asteroid, it can be smashed. Things seem to be going to plan, but they soon find out something lives on the asteroid, and their plan comes crashing down.

Experiment #025 - Topper

Stitch is having his first Christmas on Earth, and Lilo is trying to teach him about the holiday. But when Stitch sees an unactivated pod fall into a gift in the mall, he goes crazy trying to track it down. Soon he ends up stealing every gift on the island, and Lilo thinks he has become greedy. However, the truth comes out... But can they find the Experiment pod?

Experiment #228 - Melty

Lilo makes an idiot of herself in front of Keoni, so she and Stitch decide to use Jumba's Time Machine to go back and change the past. However, she may have fixed her problem, but she creates a bigger problem when Stitch destroys the Birds of Paradise hotel chasing Experiment #228 and Nani is fired from her new job. Will things work out?

Experiment #222 - Poxy

Poxy is activated one day when Pleakley eats it in his cereal! So, Lilo and Stitch must get shrunk with one of Jumba's machine, along with a buggy, and travel through Pleakley to find the experiment. However, Pleakley is captured by Gantu and is going to be sent to Hamsterviel for Poxy. Can Lilo and Stitch get Poxy and save Pleakley in time? And will they do it before they start to turn back to normal size?

Experiment #258 - Sample

#258 is activated. #258 is a sound experiment, that records sounds and plays them back to people, like a sample. Meanwhile, Stitch is worried about getting his shots.

Experiment #608 - Slugger

After Pleakley's incompetence in baseball causes Lilo, Stitch, and Stitch's cousins to lose to Mertle's team, Lilo and Mertle arrange a rematch, with Lilo's collection of Elvis records and Mertle's collection of dolls on the line. Lilo finds Experiment #608, aka 'Slugger', and decides his projectile-deflection skills would make him an excellent pinch-hitter for her team. Unfortunately, Mertle gets her own ringer in Gantu, and makes the rematch a game of basketball instead of baseball, with Slugger on the line as well! Can Lilo and the experiments win under these circumstances, or will they need help from an unlikely source?

Experiment 020: SLICK

Chaos ensues as Slick, a fast-talking experiment who can sell anything to anyone, teams up with Lilo and Stitch to sell candy bars for the Hale Kaiulu's annual fundraiser. Lilo soon learns the hard way that Slick is not designed to stop, and she and Stitch must reclaim their household items before it gets too late.

Experiment 089: SKIP

Lilo's desire to hurry and grow up is immediately satisfied when Skip, experiment 089, arrives and ages her up to a 17-year-old and then a 27-year-old. Lilo soon realizes she wants to be age 7 again because she misses out and ruins the future. She must figure out how to "reset" herself.

Experiment 267: WISHY-WASHY

Lilo learns a valuable lesson in being careful what you wish for when Experiment 267 is activated.