"The Reurn of Ploot" (Izayoi Island Rescue!, Izayoi-jima o Sukue!, イザヨイ島を救え！／さよなら、スティッチ) is the 28th episode of Stitch!-The Mischievous Alien's Great Adventure. It first aired in Japan on June 29, 2010 and in English on June 22, 2012.
The annual festival beach party is today and everyone is excited except Stitch (and we all know why). Pleakley is deciding on an outfit, but Jumba's lab bursts out with trash. Coincidentally, a garbage truck was nearby and Pleakley throws out his trash. While driving the truck, it hits a bump and the trash falls in the ocean. While sinking, the bag breaks and the trash falls out even and Experiment 505 (A.K.A Ploot, the experiment that collects trash) Jumba soon realizes Experiment 505 was gone. Back at the bottom of the ocean, 505 wakes up and begins eating the trash.
At the beach, everyone is having fun. Penny is showing off but Tigerlily in a hot swimsuit comes by and pretends that she didn't know and the boys already fell for her. Stitch is at the trash pile trying to build a robot and complains to Taro about his molecular structure. He successfully builds it and wants to play robot battle, but scares off a lot of people and is stopped by Tigerlily. Yuna also refuses and scolds Stitch for making a mess. Penny forces her goons to peddle a boat but she falls off. Before she scolds the group she finds a strange yet familiar substance on her nose. Pretty soon the whole ocean is infested. Everyone is upset except Stitch, but they really want to know who has done it. Yuna suggests Hamsterviel, and he actually appears. Yuna accuses him of polluting the water, but Hamsterviel himself claims he had nothing to do with it. He reveals his invention a robot-like Hamsterviel who shoots out green tentacles, Yuna then asks if is he kidding. Hamsterviel replies no and opens the hatch but after smelling the air and closes it again. But the robot attacks the ship. Jumba now reveals that an experiment is up to it Experiment 505: he eats the trash but releases it in the form of sludge, Jumba secretly stole him from Hamsterviel the past week. Pleakley ask how did he escape and Jumba says, "He [Pleakley] might've accidentally threw him out."
Yuna wants to go stop Ploot but Stitch doesn't want to and doesn't care if the ocean is polluted and takes a stroll. Later the smell is getting worse and worse even the yokai are weakening. Stitch goes around to find someone to play robotwars. But everyone is disgusted by the smell to do so. Jumba can't track Ploot (or any fish!). It starts to get chilly and soon snow falls. Pleakley believes it's Ploot but Jumba denies it since precipitation is way out of his control. He senses something wrong with the Spiritual Stone, they soon find Kijimunaa covered in snow. He claims the Spiritual Stone was calling him Jumba's predictions were correct). He puts his hand on the stone and translates on what it's saying. It says the island is the navel and if it's broken the body is, revealing that the Izayoi Island is the important part of the planet. Kijimunaa faints, at the house Tigerlily shows everyone that the whole world is experiencing something unusual. They run to catch the monster, Kijimunaa says that the stone also says trust in Stitch he is the greatest warrior but he's delirious so he doesn't know if it means it. Grandma reassures him that he probably does. Jumba sends out an army to capture Ploot.
Stitch wants to capture Ploot using Penny's boat but Penny stops him so she can use the boat to rent another island (not knowing that the whole world is doom). Tigerlily rents a boat to look for Ploot with Yuna and even Grandma. Stitch rebuilds Robot 2.0 now with a breathing monitor and goes underwater. He finds that Ploot is nearby when sludge starts splattering all over the screen and meets with Ploot (now really big) but the monitor cracks and the robot is destroyed. Stitch managed to get it on land but the sectors couldn't find Ploot until Grandma reconizes a giant rock that wasn't there before. Yuna and Tigerlily gear up to battle the genetic expirement. Tigerlily finds him and battles him but they have no affect on him. He rises up from the ocean with Yuna and throws her. Stitch (nearby) saves her. Tigerlily saves Jumba, Grandma, and Pleakley but instead it tries to travel out the ocean but the fishermen spot him and traps Ploot. Ploot swallows the net but Stitch goes to the rescue but is easily defeated. Stitch rebuilds his robot Robot 3.0 with jet rockets but the fuel soon runs out and the robot along with Stitch is swallowed. All hope is lost but Stitch wants to give Ploot indigestion forcing him to barf and return to normal size. Ploot returns to his normal size. The festival returns and Stitch gets another good deed and only needs one more to gain ultimate power.