It's Mertle's birthday, and she's got a brand new bracelet! But Lilo soon finds out it's got an experiment pod, though she doesn't know the number. So, Stitch goes undercover for her, and discovers it is the pod for Experiment #606. Now Lilo must get the pod back as quickly as possible; as #606 is an experiment that can suck in the entire world!

The Hula Girls have ditched Mertle for Lilo, and consequently, Lilo neglects Stitch to hang with them at the Kauai Medieval Festival. So, when Experiment #586 is activated, Stitch needs someone to capture it with. And who does he team up with? Mertle. Strangely, Stitch and Mertle are having fun trying to capture the metal eater, but this ends when it storms the Medieval Festival.

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.