Gigi

 Gigi, A.K.A. Experiment 007 and Yapper, is an illegal genetic experiment created by Jumba Jookiba. She is designed to annoy Jumba's neighbors with her constant yapping. Her one true place is with Mertle Edmonds. Gigi was voiced by Frank Welker, while Tress MacNeille did her speaking voice.

Bio
Experiment 007 was the 7th genetic experiment created by Jumba with Hämsterviel's funding. She was designed to sit, fetch 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.

Lilo & Stitch: The Series
At an unknown point, Experiment 007 was activated and found by Mertle who named her Gigi.

Mertle showed Gigi off to Lilo and Stitch, but when Gigi's yapping began to annoy Stitch, the latter swallowed her whole. Mertle then dragged Gigi out of Stitch's stomach and took her to a pet salon to get cleaned up.

Later, Mertle revealed that she was entering Gigi in the junior dog show in Honolulu. Lilo, wanting to compete with Mertle, went to Honolulu as well and entered Stitch in the dog show, claiming that he was a rare blue-furred ectoplasmic detection dog. The judges were impressed, while the other dogs looked suspicious.

Both Stitch and Gigi were entered into all the competitions. However, Stitch's temper and overconfidence caused him to lose the first two rounds. In the final competition, Mertle secretly gave Stitch very strong coffee to make the latter go crazy so that Gigi would win.

Mertle's plan was successful at first, but Gantu suddenly burst in and took Gigi. To save his cousin, Stitch took on Gantu, but got crushed when the ceiling collapsed on top of the latter. Lilo then gave Stitch more coffee intentionally, enabling Stitch to get Gigi back from Gantu and kick him out.

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 walked by Mertle and the hula girls.

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 round 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 saved from a Leroy 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 `Oe, which caused the Leroy army to shut down due to the original Leroy's failsafe.

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

Trivia

 * Gigi did not speak in Lilo &amp; Stitch: The Series. However, during the climax of Leroy & Stitch, she revealed that she could actually talk and says to Clip, "Nice one, cousin." She then says to Mertle, "Look out!" and pushes her out of the way of a Leroy's plasma blast.