Stitch is the name of the genetic experiment 626, a fictional alien character from the Lilo & Stitch films and television program.
History
As revealed in Lilo & Stitch 2: Stitch Has a Glitch, Stitch was created by evil genius Doctor Jumba Jookiba with the genes of the galaxy's strongest and most ferocious creatures, but when the experiment was finished, Jumba was disappointed to see how cute and fluffy he was. Nevertheless, Jumba soon sees 626's destructive potential and begins to charge Stitch's molecules. However, before Stitch is fully charged, both he and Jumba are captured by police officers of the Galactic Federation.
626 was then sentenced by the Grand Councilwoman to life in exile on a desert asteroid and was escorted by Captain Gantu. Stitch escapes and crash-landed in Kaua'i, Hawaii. Disguising himself as a dog, 626 was adopted by a little girl named Lilo, who names him "Stitch".
Although at first he only wanted to use the girl as a human shield from Jumba and Agent Wendy Pleakley, Stitch slowly developed feelings for her, to the point where he saved her life from Gantu.
Stitch! The Movie
After the capture of Jumba, who had moved in with Lilo and her sister along with Pleakley, 626 discovered the remaining 623 genetic experiments locked in a crate, in dehydrated pods. In order to rescue Jumba, Lilo and 626 instituted a trade with Doctor Hàmsterviel, Jumba for the experiments, which resulted in the freedom of said experiments and the capture of Lilo and Stitch. Hàmsterviel then tried to clone Stitch, in a process that would have most likely destroyed him and would have done so, if it weren't for the interruptions of the previously activated Experiment 221 (Sparky), who created a power surge in order to shut down the cloning equipment. Stitch then rescued Lilo and landed Hàmsterviel's spaceship back in Kaua'i, where the Grand Councilwoman waited to arrest Hàmsterviel.
Lilo & Stitch: The Series
Currently, Stitch resides in Lilo's house, continuing to disguise himself as a dog in order to conceal his identity from humans. Along with Lilo, he re-captures and rehabilitates Jumba's genetic experiments.
Abilities
Experiment 626 has a variety of special abilities. He is fire and water-proof. Stitch can also lift objects 3000 times his weight, a running joke throughout Stitch! The Movie and Lilo & Stitch: The Series being that he can't lift an ounce more. He also has very sensitive eardrums, that when exposed to loud noises can cause temporary deafness. His eyes are programmed to pick up infrared and ultraviolet light, as well as visible light, and he can filter out one or the other if need be. He also can act as an audio amplifier and/or microphone, though whether Jumba intended this or not is disputable.
Disney Adventures
According to the Disney Adventures comic "Experiment 626", he was created with the genes of the galaxy's strongest and most ferocious creatures, but somehow the genes of a puppy got mixed into the batch. Stitch was created using the so-called "Jumbatron 6000", apparently some kind of cloning or splicing device. After creation, 626 was determined a failure and Jumba continued work on his next experiment. 626 promptly proved Jumba wrong by causing various acts of mayhem, resulting in panic among the populous.