Stitch (also known by his species name/”birth” name Experiment 626, pronounced “six-two-six”) is a fictional character in Disney’s Lilo & Stitch franchise. An illegally-made, genetically-engineered, extraterrestrial lifeform resembling a blue koala, he is one of the franchise’s two title characters, alongside his adopter and best friend Lilo Pelekai, and its primary protagonist. Stitch was created by Lilo & Stitch co-writer and co-director Chris Sanders, who also voices him in all Western-produced media that he appears in, while Ben Diskin voices the character in the English versions of the Eastern-produced television series Stitch! and Stitch & Ai.
Stitch in his disguised “Earth dog” form (lower arms, antennae and spines retracted), the most-often seen form of the character
In the franchise’s chronology, he was originally created by Dr. Jumba Jookiba to cause chaos across the galaxy. Stitch is marked by his mischievous behavior, which endeared him to Lilo, who adopted him as her “dog”. Through Lilo’s beliefs in the Hawaiian concept of ʻohana, meaning family, Stitch developed from an uncaring, destructive creature to a loving, more self-conscious being who enjoys the company of his adoptive family on Earth. He became a firm believer of the ʻohana concept, and with the help of Lilo applied it to reform Jumba’s 625 prior experiments, nearly all of whom Stitch treats as his “cousins”.
Source : https://en.m.wikipedia.org/wiki/Stitch_(Disney)