Poxy

 Poxy, A.K.A. Experiment 222, is an illegal genetic experiment created by Jumba Jookiba. He is designed to enter the bodies of and disease popular planetary leaders. He was captured by Gantu, but was rescued in "Snafu". According to a bonus feature game in Lilo & Stitch 2: Stitch Has a Glitch, his one true place is fixing health problems. Poxy is voiced by Frank Welker.

Bio
Experiment 222 was the 222nd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to enter the bodies of popular planetary leaders. The disgusting symptoms (purple pimples, smelly feet, swollen eyes and uncontrollable burping) which 222's presence would cause would result in the disgusted public revolting against the infected leader.

222 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 222's pod landing in a sugar crop.

Lilo & Stitch: The Series
222's pod was caught up in the machines used to extract sugar from the crop. The pod eventually made its way into Pleakley's cereal, where the milk activated the experiment before it was eaten with the cereal by Pleakley. The latter quickly became infected by 222's disease with the above symptoms.

Believing that human doctors could help him, Pleakley went to the nearest health clinic. While he sat in the waiting room to be admitted, Gantu showed up looking for the experiment. He then noticed a sick Pleakley, and chased after him upon realizing he was afflicted by 222.

Fortunately, Lilo and Stitch, who had followed Pleakley to the clinic, managed to save him by subduing Gantu with laughing gas. While Gantu was incapacitated, Pleakley was rushed out of the hospital while Lilo and Stitch convinced him that Jumba had a way of removing 222 from Pleakley's body.

Using Jumba's shrink ray, Lilo and Stitch shrunk themselves to microscopic size and entered Pleakley's body to find and capture 222. After a long chase through Pleakley's body, Lilo and Stitch were able to capture and extract 222 when the latter became stuck in Pleakley's earwax.

Later, Gantu came and kidnapped Pleakley. Before Lilo and Stitch had safely made it outside of Pleakley's body with 222, Gantu took a beating from a well but delusional Pleakley. When Gantu attempted to crush Pleakley afterwards, the former was shrunk to microscopic size and captured. Lilo then planted 222, christened Poxy, inside Gantu, who fell deathly ill from the experiment.

As Gantu was healthy in later episodes, it can be presumed that Poxy was extracted and sent to Hämsterviel, then back to Gantu in "Woops" along with Gantu's other captive experiments.

Poxy reappeared in "Snafu", and was freed along with Gantu's other captive experiments by Lilo, Stitch, and several other experiments in a rescue mission.

Leroy & Stitch
The first 624 experiments, including Poxy, 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.

It is unknown whether or not Poxy participated in the following battle between the experiments and the Leroy clones.

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.

Personality
Poxy is very devious, yet carefree. He never really worries about anything and is seen multiple times messing with Lilo and Stitch. His worry-free attitude might be a result of his great confidence. To him, everything seems to be a nuisance than an actual threat because while infecting somebody, he is not harmed, not even by antibodies. So, he just makes himself right at home inside his host.

Trivia

 * In "Poxy", Poxy was microscopic size. However, in "Snafu", he was the standard size of an experiment. This might imply that Poxy can change size while using his function as a germ, but it is possible that his container acted like a lens and magnified him to a noticeable size, as he disappeared when he was released.
 * Poxy's pod color is green.
 * Poxy is described by the experiment computer screen that says "Experiment 222 Primary function: Transmit a disease illness to planetary leaders."
 * Poxy did not appear in Leroy & Stitch, most likely due to his microscopic size.