Stitch is the name of the genetic experiment 626, a fictional alien protagonist from the Lilo & Stitch films and television program. Originally created to cause chaos across the galaxy, he is marked by his short temper and mischievous behavior, traits that endear him to his friend Lilo, who adopted him as her puppy dog. He is voiced by his creator and the film's co-director, Chris Sanders.
626 is then sentenced by the Grand Councilwoman to life in exile on a desert asteroid and Captain Gantu escorts him. Stitch escapes and crash-lands in Kaua'i, Hawaii. Disguising himself as a dog (although he actually looks like a koala), 626 was adopted by a little girl named Lilo, who names him "Stitch".
Stitch is trained by Lilo to be good, using Elvis Presley as a model for his behavior. Lilo's efforts prove to be fruitless at first, as Stitch is unable to suppress his destructive programming. Nevertheless, Lilo enjoys her new "puppy". Although at first he only wanted to use the girl as a human shield from Jumba and Agent Pleakley, whose mission is to capture the fugitive experiment, Stitch slowly develops feelings for Lilo, to the point where he saves her life from Gantu. After his heroics, the Grand Councilwoman allows Stitch to serve his exile on Earth with Lilo as his warder, citing her dog adoption certificate (subsequently, Lilo seems to have become not only a best friend but also a sister figure to Stitch).
In Lilo & Stitch 2: Stitch Has a Glitch (set shortly after the first movie), Stitch is living well and is reasonably well-behaved (although still hot-tempered and mischievous) with the exiled Jumba and Pleakley in Lilo's house until he begins malfunctioning. Since he was not fully charged after his creation, Stitch experiences periodic glitches that have him reverting back to his original destructive programming, appearing to suffer from a "fit" or "seizure". Seeing this, Jumba strives to create a proper charging chamber for Stitch. Not wanting to hurt anyone and not knowing about Jumba's plan, Stitch attempts to leave Earth for a remote planet, while Lilo, Jumba, and the others desperately try to have him return so they can recharge him. Although they are too late when they place him in the recharging pod, Stitch seems to be revived by Lilo's love, in accordance with her belief that love is more powerful than death.
In Stitch! The Movie, 626 discovers the remaining 625 genetic experiments locked in a crate, in the form of dehydrated pods. In order to rescue a kidnapped Jumba a trade between Dr. Jacques von Hämsterviel and Jumba for the experiments is organized, but it instead results in the freedom of the experiments and the capture of Lilo and Stitch. Hämsterviel then tries to clone Stitch but he was rescued by Experiment 221 ("Sparky"). Stitch then rescued Lilo and landed Hämsterviel's spacecraft back in Kaua'i, where the Grand Councilwoman waited to arrest Hämsterviel.
In Lilo and Stitch the series, Stitch and Lilo have to capture Jumba's experiments, turn them from evil to good, and find them a home. Along the way, he meets his match Experiment 627 who is tougher than him. Stitch eventually defeats him. He also is effected by three experiment powers: Amnesio wipes out his memory, Spike makes him goofy and Babyfier turns him into a baby. Hoever, the powers wear off. He also meets Angel (Experiment 624) who is introduced as a love interest for Stitch. Angel eventually fell in love with Stitch. She was captured but later rescued by Lilo and Stitch.
After they have successfully captured all the remaining experiments in Leroy & Stitch, The Grand Councilwoman offered Stitch the chance to become the captain of the Galactic Armada and its new flagship, The BRB (Big Red Battleship) 9000. However, that would require Stitch to be separated from Lilo. Not wanting to make Lilo sad, he chooses to return to Kaua'i. However, Lilo tells him he should go. Before he leaves with Jumba and Pleakley, Lilo gives him a necklace with a tiki of the god Ku Tiki to give him strength. She also gives Pleakley a rock, and Jumba an Elvis record. When Gantu breaks out Dr. Hämsterviel in an action of frustration, Stitch is sent on his first mission to capture the evil rodent once more. But when he arrives at Galactic Defense Industries, Stitch faces off against a new experiment - Leroy, who is an enhanced clone of Stitch. Stitch fights well and is about to beat Leroy when Pleakley shows up unexpectedly, allowing Leroy to take advantage of Stitch's lapse in concentration and beat him. He is placed in a cage and sent with Jumba and Pleakley heading towards a black hole. After they are sent towards the black hole, Leroy heads off towards earth to capture all of the other experiments for Hamsterviel. Later, Stitch, Jumba, and Pleakley escape from the black hole, and arrive on the planet Turo. There they rescue Lilo, 625 (now known as Reuben), and Gantu, in whose spacecraft they fly back to Earth to assist the other 624 experiments in the defeat of an army of Leroys. Now, with Leroy defeated, Stitch, Jumba and Pleakley return to Earth with Lilo, realizing family is more important than spaceships, laboratories, and prestige.
While explaining his creation to the Galactic Council early on in Lilo & Stitch, Dr. Jumba gives the following rundown of Stitch's powers: "He is bulletproof, fireproof, shockproof and can think faster than [a] super computer. He can see in the dark and can move objects 3,000 times his size. His only instinct - to destroy everything he touches!"
In the original Lilo & Stitch movie, Jumba claimed that Stitch's "destructive tendency was taking effect", and that he would be irresistibly drawn to large cities to "back up sewers, reverse street signs, and steal everyone's left shoe."
Although we rarely see Stitch shot at with a bullet, he does survive the crash of his spaceship with only a scratch, is only briefly stunned by a fall of several thousand feet, and has to be run over by three tractor-trailers in succession to be knocked out. As for fireproof, he does drive a tanker truck of gasoline into a volcano and ends up only a little singed. Weapons fire from plasma guns seems to cause him discomfort, although he can hold it in his hands long enough to throw the plasma back at his enemies. Thinking faster than a supercomputer is harder to quantify, but he does figure out how to escape from captivity fairly quickly, builds a model of San Francisco after only glancing at a postcard; grabs a crossword puzzle from the table and finishes it in about 7 seconds; builds a bomb out of a plasma-bolt, a doll and a roller skate; operates automobiles with ease; builds a "bucking bronco" out of a toaster, a vacuum cleaner, and a lamp; and generally picks up quickly on what is happening around him. However, his ability to lift objects 3,000 times his own size and weight is seen several times throughout the franchise, including incidents where he lifts a building off its foundation and hurl it, he picks up a descending blast door, and another where he hits Dr. Jumba with a thrown Volkswagen Beetle (shouting gleefully, "blue punch buggy! No punch back!"), yet another he plays the airplane along with 234 people inside like a giant frisbee, and again when he stops an 18-wheeled tanker of gasoline dead in its tracks. This ability is sometimes joked about in the later series; for example, in Stitch! The Movie, Hämsterviel, while physically restraining Stitch for a cloning experiment, counters Stitch's strength with restraint devices, that are equal in strength themselves, as Hämsterviel loudly declares, to "three-thousand and one!" times Stitch's own weight.
His greatest weakness is his inability to float or swim due to his dense molecular structure, which causes him to sink like a stone in water. Another weakness is the fact that his super-sensitive hearing can lead to temporary deafness when exposed to sonic blasts. His third and arguably greatest weakness, is if a macadamia nut and a tennis shoe goes in his mouth, all of his special abilities will be completely erased, including his strength and dexterity. At this point, the only way to restore his abilities is to retrain him from scratch. At the beginning of the first movie, Stitch had an instinctive Hydrophobia (fear of water) and avoids pools but was able to overcome it because of Lilo's influence over him. His claws are able to grip anything: pads on his feet and paws contain a sticky substance allowing him to adhere to almost any surface and scale buildings and walls. His skeletal system is very flexible, allowing him to put his feet into his mouth and become a rolling ball/buzzsaw, while his legs are powerful enough to enable him to jump several feet into the air. His eyes can pick up infrared and ultraviolet light as well as visible light and he can filter out one or the other if necessary. He can see in normal vision (during this mode, his eyes appear black in color), night vision (which is green), infrared (red), ultraviolet (purple, which allows him to seen animals that have left their scent marks, unlike all past alien experiments), and in the series he displays the ability to 'zoom in' (and apparently sees with a head-up display). He can grab a pure plasma burst in his hand and hurl it back (with some pain), he catches it shoves it in his mouth for it to get to critical point and unleashes it as a huge plasma cannon blast; capable of destroying a full house in one blast. He also can act as an audio amplifier, radio and/or microphone, illustrated when he can put his finger on a record player and the music comes out of his mouth, but he walks around being a portable radio; he opens his mouth and pops his antennae out which receive radio signals and you can listen to radio. He can instantly regrow his fur in the series, but it's unlikely this is an actual ability. He has an acute sense of smell and hearing as well as some ability to receive and transmit microwave radio energy via a pair of antennae on his head. He has displayed an ability to fight in hand-to-hand combat easily with his four arms, but has also demonstrated similar ability using only two in the series.
Also, once in the movie when he and Lilo are captured, Stitch was able to simply go through the glass, this was seen once in the franchise, whether this is a official ability remains to be seen.