Stitch doesn't know how to take care of anything that is his or belongs to others. This reaches a climax after he breaks the shake machine at the Rental Shack, getting Nani into a lot of trouble with Mr. Wong. When "Richter" (experiment #513) is activated, the island is rocked with potentially devastating quakes, ones that could destroy the entire planet. Lilo and Stitch manage to chase down Richter and put a stop to his destructive quake making. In the end, Stitch learns to value what he has and things that belong to others. Richter is repurposed to replace the broken shake machine at Nani's rental shack.

Experiment #375 is activated, a phantom-like experiment designed to inhabit and "animate" inanimate objects. When Phantasmo gets loose in Lilo's house it inhabits Lilo's doll Scrump and creates all sorts of problems for which Stitch gets blamed. Lilo is the one who stands by her friend, believing him to be innocent. After Lilo holds a "trial" of Stitch's peers, (Lilo's toys & dolls) the truth comes out that Stitch is not the one to be blamed. In the end Phantasmo is repurposed to operate/inhabit the animatronic characters at Maki McCaw's Hometown Luau.

Lilo is feeling unhappy with herself after Mertle gets a big fancy hairdo. When Lilo comes across a hair-eating experiment #177 (Clip), she decides to get revenge on Mertle by placing the experiment in Mertle's bedroom with designs on ruining her new hairdo. Lilo's plan backfires and Clip eats all of Mertle's Mom's hair instead... and worse yet, Clip has escaped and is loose on the island. Lilo and Stitch must track down Clip before everyone on the island goes bald. Lilo learns to accept herself the way she is and feel good about how she looks. Clip ends up being the perfect answer for problems at the local salon, where she is repurposed, giving customers cool new haircuts.

Experiment 254 is a stink bomb whose stench will make any area uninhabitable for decades. But he's also cute as the dickens, and everyone who sees him falls in love with him... everyone except Stitch, who resents all the time Lilo's spending with "Mr. Stenchy". Stitch gets so jealous of 254 that he lets him get captured by Gantu! Losing Mr. Stenchy makes Lilo so sad that Stitch can't take it anymore; he decides to re-capture Mr. Stenchy. Stitch sneaks aboard Gantu's ship to retrieve Mr. Stenchy... but even Gantu has fallen for the little guy!

It's the greatest time of year: Halloween! As Lilo dresses up in a gory costume (hula attire with a rubber ax through her head), Nani tries to ready the house for trick-or-treaters. Sadly, Lilo and Nani's house never gets any trick-or-treaters, a fact that Nani is determined to change. Meanwhile, Experiment 300 is activated in the woods.

For her birthday, Mertle gets a bracelet... with an unactivated experiment pod attached to it! Lilo notices the experiment pod and realizes she must get that bracelet from Mertle. Soon she and Stitch are practically stalking Mertle, but are constantly being foiled by a local police officer. Stitch finally is able to discern the number on the pod: Experiment 606, a black hole experiment that will suck in the whole world!