Ploot

Ploot, A.K.A. Experiment 505, is an illegal genetic experiment created by Jumba Jookiba. He is designed to flood entire cities with toxic sludge created from trash and pollution he collects. His one true place is cleaning up litter and pollution.

Bio
Experiment 505 was the 505th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to collect pollution and trash, growing bigger as he collected more. 505 would convert the pollution he collected into toxic sludge, and when he collected enough, he would spread it across the nearby area.

505 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
505's pod eventually made its way into a bag of trash, which was thrown over a cliff into the underwater grotto, activating 505. 505 first began collecting pollution in the grotto, then he started collecting trash all around town. Lilo and Stitch, unaware of what 505, whom Lilo named Ploot, was collecting the pollution for, decided to let him carry out his primary function rather than attempt to stop him.

However, Ploot eventually collected enough trash to grow into a monstrous form, and began spreading toxic sludge around the island despite Lilo and several experiments' best efforts to stop him.

Ploot eventually kidnapped Lilo, but was defeated when Stitch used natural air freshener to reduce Ploot to his original size.

Ploot was then captured and found a one true place cleaning up litter.