Gigi

Gigi, A.K.A. Experiment 007 and Yapper, is an illegal genetic experiment created by Jumba Jookiba. She is designed to sit, lie down, fetch, and annoy Jumba's neighbors with her constant yapping. Her one true place is with Mertle as her pet.

Personality
While Gigi fulfilled the purpose she was programmed for, which in her case was to annoy people with her constant barking, this is not a defining feature of herself. Most of the time, she is well-behaved and appears to look and act like a normal dog: barking, fetching, and listening to orders. She can be distinguished from a real dog by her ability to talk. She is affectionate to those she likes, licking Mertle's face and complimenting Clip on eating a Leroy clone's fur off. She is also loyal and brave, pushing Mertle out of the way of a plasma blast. She holds the ideal of family and ʻohana very close, having convinced Mertle to join Lilo's ʻohana because she wanted to be in it as well, and seems to get along well with her cousins.

Lilo & Stitch: The Series
Experiment 007 was the 7th genetic experiment created by Jumba with Hämsterviel's funding. She was designed to behave like a typical "good dog" and annoy Jumba's neighbors with her constant yapping. 007 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.

At an unknown point, Experiment 007 was activated and then later adopted by Mertle, who named her Gigi.

In the episode "Yapper", Mertle showed Gigi off to Lilo and Stitch, and revealed that she was entering her in a dog show contest in Honolulu. However, when Gigi's yapping began to annoy Stitch, the latter swallowed her whole. Mertle screamed in horror until Lilo pulled Gigi out of Stitch's stomach and gave her back, albeit covered in slobber. Enraged, Mertle called Lilo and Stitch "riffraff" and took Gigi to a pet salon to get her cleaned up.

Wanting to win Mertle's friendship by beating her Gigi in a reasonable contest, Lilo traveled to Honolulu with Jumba and Pleakley. There, she entered Stitch in the same dog show, claiming he was a rare blue-furred ectoplasmic detection dog to impress the judges.

Lilo and Mertle engaged in an unfriendly rivalry and entered their "dogs" into all the competitions, which took place the next day. However, both Stitch's temper (when he fought with a contestant's dog after the latter sniffed him) and overconfidence caused him to lose the first two rounds. In the final competition, Mertle secretly gave Stitch extra strong coffee to make the latter go crazy so that Gigi would win.

Mertle's plan was successful at first, but then Gantu suddenly burst into the premises searching for her "dog". Stitch impulsively attacked Gantu, who fired his plasma gun uncontrollably, but a stray plasma blast caused the ceiling to collapse on top of Stitch. Gantu then took Gigi from a terrified Mertle, after which she complained to Lilo.

Because Gigi was Stitch's cousin, Lilo promised to save her from Gantu. She then gave Stitch more coffee intentionally, enabling the latter to defeat Gantu and get Gigi back safe and sound.

Grateful but indignant, Mertle gave the "Best in Show" trophy to Lilo. However, when Lilo saw how much Mertle truly cared for Gigi, the former decided to leave Gigi with Mertle.

Gigi reappeared in "Amnesio", being accompanied by Mertle and the hula girls while Lilo attempted to invite them to her birthday party.

In "PJ", Gigi and a couple of regular dogs attacked Lilo's substitute teacher wearing squeaky shoes shaped like dog biscuits, which was one of PJ's many pranks.

Leroy & Stitch
Gigi was seen being walked by Mertle, the latter stopping to taunt Lilo before moving on.

Later, the first 624 experiments, including Gigi along with Mertle, 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.

During the following battle between the experiments and the Leroy clones, Mertle with Gigi tried to avoid attacking Leroys. When Mertle and Gigi were both saved from a Leroy clone by Clip, Gigi revealed her ability to speak and her status as an experiment, then pushed Mertle out of the way of a Leroy's plasma blast.

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 ʻOe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.

Following the battle, Gigi declared that she wanted to be part of Lilo's ʻohana, convicing Mertle to join it with Gigi.

Trivia

 * Gigi was first revealed in a DVD bonus feature of Stitch! The Movie in the experiment gallery.
 * Gigi is one of the ten known experiments named by someone other than Lilo, the other nine being Elastico, Yaarp, Hammerface, Heat, Thresher, Plasmoid, Morpholomew, Shrink, and Leroy.
 * She is also one of the six known experiments to be rehabilitated by someone other than Lilo and Stitch, the other five being Elastico, Yaarp, Spike, Frenchfry, and Snooty.
 * Her episode is named "Yapper" after the nickname Lilo gave her, but she is officially "Gigi" on the experiment name list in Leroy & Stitch.
 * Gigi's pod color is white.
 * Gigi is described by the experiment computer screen as, "Experiment 007. Primary function: Annoying with barking forces."
 * Her number is a reference to the secret agent number of the legendary, although this is just a mere coincidence, as Gigi shares no real similarities with James Bond.
 * Gigi never spoke in Lilo & Stitch: The Series. However, during the climax of Leroy & Stitch, it is revealed that she can speak English very well and says to Clip, "Nice one, cousin." She then says to Mertle, "Look out!" and pushes her out of the way of a Leroy clone's plasma blast.