Spooky

Spooky, A.K.A. Experiment 300, is an illegal genetic experiment created by Jumba Jookiba. He is designed to scare and terrorize his victims by morphing into their worst fears. His one true place is greeting and scaring trick-or-treaters on Halloween, and (for the rest of the year) haunting the old, abandoned mansion.

Personality
Spooky causes chaos by fulfilling the purpose he was programmed for: terrifying his enemies with their worst fears. However, he went further by directly harming his victims, aside from just scaring them, and seems to be more dangerous than most experiments. This is proven when he nearly drowned Stitch and scared Lilo off a high pillar to her death, which was thwarted when Stitch saved her. Originally malicious and slightly sadistic, he often chose to not only provoke fear, but cause other mental trauma such as sadness and terror in his victims. He tends to slither and hiss like a snake, despite his most common form of being a blob. When people are brave enough to stand up against his scares, Spooky becomes annoyed and apparently powerless against them. However, after being reformed, Spooky only scares people for fun on Halloween. He is also loyal and helpful to his friends, joining Stitch's rebellion to fight off Gantu.

Lilo & Stitch: The Series
Experiment 300 was the 300th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to terrify enemies into submission by morphing into their worst fears. 300 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.

All of the experiment pods were released and scattered across the island of Kauai, with 300's pod landing on a house roof.

On Halloween night, a gust of wind caused 300's pod to roll down the roof's rain gutter and fall into a rain barrel, activating the experiment. 300 then noticed a mouse and scared it off by turning into a wild cat. When a dog attacked 300 because of the cat form, the latter frightened the dog away by turning into a dogcatcher, then fled the scene in his elastic form.

300 shortly after attacked a children's Halloween party at Lilo's hula school, scaring Mertle and the hula girls off by turning into a headless Lilo, then terrifying Moses by turning into a giant spider.

When Lilo and Stitch later discovered the disastrous party and Stitch entered the kitchen to raid the fridge, 300 locked himself in the kitchen with Stitch and almost drowned the latter by turning into floodwaters. However, 300 was forced to retreat through an air vent when Lilo noticed his presence.

Sometime later, 300 arrived at the Pelekais' house, where he terrified Nani by turning into Cobra Bubbles and claiming he came to take Lilo away. However, when Lilo and Stitch returned to the home and noticed Cobra to be 300 from his hissing voice, they exposed 300, named Spooky, as an imposter, forcing him to retreat.

Lilo, Stitch, Jumba and Pleakley followed Spooky into the old mansion, where he surprised and terrorized Lilo by turning into a clown. Stitch unintentionally fell into an indoor swimming pool after Lilo's shriek startled him. Spooky then chased after Lilo in his clown form, scaring her to the point where she clung to a small ledge screaming for help.

While Stitch was sinking in the pool, Spooky defeated Jumba and Pleakley by turning into their worst fears: Pleakley's mom and Jumba's ex-wife. However, Stitch eventually overcame his aquaphobia by singing "Aloha `Oe" (a song that Lilo had taught him as a coping method), and emerged from the pool. He then rescued Lilo in the nick of time.

When Spooky noticed that Stitch had faced his fears, and was thus unaffected by the former's other scary forms, Spooky turned into a bat and attempted to escape up the chimney, but was ambushed and captured in a containment orb by Stitch.

Spooky was then found a one true place scaring trick-or-treaters on Halloween, and (on other occasions) haunting the abandoned house.

In "The Asteroid", Spooky was one of the six experiments that Stitch convinced to come with him and Lilo to save Earth from an approaching asteroid (Spooky morphed into one briefly for clarification). During the journey, Kixx kicked the back of Spooky's seat, causing the latter (using his ability to morph into nightmarish forms) to retaliate. Spooky later attempted to use a monstrous form to scare Pleakley into giving him free soda, but Pleakley only replied with an order for Spooky to return to his seat.

Spooky was one of the experiments in "Checkers" that joined Stitch in a rebellion against Gantu.

Leroy & Stitch
The first 624 experiments, including Spooky, were rounded up by Leroy and taken to a stadium to be destroyed. However, Lilo, Stitch, Jumba, Pleakley, Reuben and Gantu arrived before the experiments could be destroyed.

Spooky participated in the following battle between the experiments and the Leroy clones by using nightmarish forms to scare Leroys.

However, the Leroys soon gained the upper hand in the battle, but were defeated when Lilo, Stitch, Reuben and several other experiments performed the song "Aloha `Oe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.

Stitch! anime
Spooky made an appearance in the Stitch! anime when Hämsterviel sent him along with Toons to scare the children of a summer camp. It is shown that he uses a form of telepathy to read his victim's mind and discover their fears. In "Shogun", it is shown that Spooky was dehydrated back into an experiment pod and locked in Jumba's vault.

Forms
Spooky has morphed into many forms. These include:
 * A wild cat
 * A dogcatcher
 * A fat, elastic, slug-shaped version of his true form
 * Headless Lilo
 * A giant spider
 * Floodwaters
 * Cobra Bubbles (Nani's worst fear)
 * A clown
 * Mrs. Pleakley (twice) (Pleakley's worst fear)
 * Jumba's ex-wife (twice) (Jumba's worst fear)
 * A water monster
 * A twister
 * A Pupil-Eating Pass Monkey-like creature
 * A bat
 * A giant python
 * An asteroid
 * Gantu
 * A spiky, sea urchin-like fruit
 * A version of his true form with massive fangs
 * A large, nightmarish, muscular version of his true form with an alligator-like snout
 * A Goo Gobbling Booger Beast (from The Origin of Stitch)
 * A zombie
 * Angel (when she's angry at Stitch)
 * A Tigerlily dinosaur-like creature

Trivia

 * Spooky bears a great resemblance to Oogie Boogie from The Nightmare Before Christmas.
 * Spooky has glowing, olive-green eyes instead of black ones like most of the other experiments.
 * Spooky's disguises can be seen through them by his glowing green eyes and hissing voice.
 * Jumba also referred to Spooky as X300 and mentioned that his impression of Jumba's ex-wife is frightening.
 * Spooky's pod color is green.
 * Spooky is described by the experiment computer screen as, "Experiment 300. Primary function: Morphs into the victim's worst fear."
 * Spooky's powers and abilities resemble the Boggarts in the Harry Potter series, as they are able to turn into their victims' worst fears.