The below description is taken from LEGO.com.
Stitch, an alien, is the only creature of his kind in existence. He is the result of an illegal genetic experiment by the mad scientist, Jumba, who simply refers to him as “Experiment 626.” Although Stitch appears to be harmless-small, furry and six-legged, his very existence is an abomination to all that’s decent in the galaxy. Jumba engineered Stitch as the ultimate fighting machine. He is abnormally strong, virtually indestructible, smarter than a supercomputer…and very mischievous. He feels compelled to destroy everything in his path and cannot resist his programming…that is, until he finds the one thing that he has never known before: what it feels like to be a part of a family.