Stitch escaped captivity to Earth, where he was adopted and taught of ohana by Lilo.
When Skipper came to Kauai, he explained his and Jumba's past to Lilo and Stitch, including the creation of Experiment 628. Cobra later arrived to inform them that Hamsterviel was indeed on Kauai somewhere, and Lilo, Stitch and Skipper left on a manhunt for Hamsterviel's hideout.
During the search, Stitch separated from Lilo and Skipper so that he could hang out with Angel. Suddenly, the two heard Lilo and Skipper scream. They rushed to the scene, only to find Lilo and Skipper unconscious in the aftermath of an attack by 628.
Stitch and Angel rushed Lilo and Skipper back to Jumba's ship. There, Jumba explained to Stitch that due to 628's attack, some time after Lilo and Skipper awoke, they would inevitably transform into genetic experiments.
The next night, Lilo and Skipper transformed into experiments as predicted, leaving Stitch guilty and upset that he was not there for Lilo, despite Angel's attempts to comfort him. The next day, when Jumba tested Lilo and Skipper's new powers, Stitch was tasked with training Lilo. While they were testing Lilo's telekinetic abilities, Stitch found that he was becoming increasingly attracted to the now-experiment Lilo, much to his shock.
That night, Skipper awoke Lilo, Stitch and Angel to reveal that he had discovered Hamsterviel's hideout. The four spent the rest of the night and most of the morning planning an attack on the hideout, until Gantu and Reuben arrived.
They explained what had happened to Lilo and Skipper, before launching their attack on Hamsterviel's bunker that night. They split into two teams, with Stitch's team going in the front door, and making their way through the bunker to the control room, where they met up with the other team.
However, once they reached there, they were confronted by Hamsterviel and his new experiment, Smasher, who easily shrugged off the experiments' attacks. Eventually, as the experiments began to tire and their attacks became weaker, Smasher attempted to kill Stitch by impaling him with a projectile bone.
As Lilo rushed to a dying Stitch's aid, she telekinetically stopped the bleeding from the wound, before Stitch passed out from blood loss.
When Stitch awoke, Hamsterviel fled the bunker and revealed a bomb that would destroy the bunker and kill everyone in it if they didn't stop it. Skipper determined that the bomb was touch-activated and sacrificed himself to stop it, leaving everyone devastated, especially Angel. When Stitch and the others returned home, Jumba and Stitch found a note from Hamsterviel, revealing that he had captured Reuben and would use him to create his next experiment.
Jumba and Stitch decided that they had no time tonight to consider a rescue mission, and went to bed. The next morning, Stitch tried to cheer up a saddened Lilo and Angel, without success. They decided to spend the day at the beach, where Lilo and Angel used Lilo's telekinetic powers to help Stitch swim. Stitch was at first reluctant due to his fear of water, but quickly began to enjoy himself.
Stitch is a blue, koala-like experiment with large rabbit-like ears, a wide mouth, a round nose, black eyes, a small, short, stubby tail, two nose wrinkles, one chin wrinkle, three tuffs of sharp hair on top of his head and on his chest as well as two extra, retractable arms, three retractable spines that run down his back (the first spine is the shortest, then longest, then medium), sharp retractable claws on his front and back paws and two retractable antennae on his head.
Stitch can think faster than a supercomputer, he is fireproof and bulletproof, can hear in different hearing levels, can see in the dark, can jump very high, can climb up walls and walk on ceilings, can roll into a ball, have super sight and hearing and lift objects 3000 times his own weight (but not an ounce more).
One of Stitch's few weaknesses is water; he cannot swim and will easily drown due to his great molecular density. This weakness also lead to Stitch developing hydrophobia (a phobia of water). It is also shown that if Stitch consumes two different elements that form to create a particular chemical compound, all of his physical training will be wiped. As Stitch is also 62% Snootonium, if this Snootonium is drained from his body, he will become temporarily exhausted from dehydration.