Melty is a rather simple-minded experiment, taking enjoyment in melting anything in sight, even when he's captured. One of his great advantages is that he will not be rendered powerless if his snout gets wet, as he is shown to be able to attack while underwater. He is also shown to be easily irritated and rather blunt, but is loyal to those who win his trust. Since he can liquefy things to a chocolate consistency, he may have a fondness for s'mores.
Experiment 228 was the 228th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to use his blue energy blasts to melt enemy fortresses, weapons and transportation. 228 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 228's pod landing in a palm tree.
When a gust of wind blew 228's pod out of the tree, a dog found it on the ground and took it back to its home. There, the dog dropped the pod into its bowl of water, activating 228, who proceeded to melt the house.
Prior to catching 228, named Melty, Lilo fell into a mud puddle and made an idiot out of herself in front of Keoni. She and Stitch later decided to use Jumba's time-traveling surfboard to go back in time and change the past.
In several alternate timelines created by Lilo and Stitch meddling with time travel, Melty's fate was different:
- In one timeline, Lilo barely avoided embarrassing herself by falling in the pool of mud, but Stitch's change of action caused Melty to melt the hotel, and he was caught in a fashion similar to Sparky. As a result, Nani was promptly fired from her job, causing Lilo and Stitch to start over.
- In the next timeline, Lilo easily avoided her previous mistake, but when Stitch tried to react his original steps, he accidentally threw off the balance of a falling tree, which destroyed Officer Kahiko's car, therefore having him throw Lilo and Stitch in prison.
- In the third timeline, Lilo caused a chain reaction: she laid her hand against a palm tree and startled a butterfly that got eaten by a fish; an eagle then snatched the fish and dropped it onto a ship's window, which distracted a captain and caused his cruise ship to crash into the hotel, but Melty's fate was unknown in this timeline.
- In the fourth timeline, Melty's fate was unknown, as Stitch forgot to turn on the paradox inhibitor, therefore causing him and Lilo to meet themselves.
- In the fifth timeline, Melty was unintentionally hurled into the ocean, where his melting blasts opened up a volcanic fissure in the ocean floor, causing a tsunami to form and destroy part of Kauai.
- In the sixth timeline, Melty was captured exactly like the original, but Stitch caused a chain reaction this time: he blew off a feather that fell onto his arm, causing the feather to land on an unstable coconut, which bounced down a hill, got whacked into the air by an elderly golfer, and hit the roof of Gantu's ship with a loud thud, waking Gantu up. When Experiment 625 then revealed Melty's activation to Gantu, the latter searched for the experiment at the hotel and wrecked it before coming to the Pelekais' house. After Melty melted his containment orb and their entire house, Gantu recaptured him. The time-traveling surfboard was melted as well, causing future alternate timeline Jumba (whom Lilo and Stitch accidentally met when unintentionally going forward in time) to go back and give them a new time-traveling surfboard.
- In the final timeline, and one corresponding to the original, Lilo and Stitch merely imitated their previous actions, but this made Lilo forcibly embarrass herself in front of Keoni again. They captured Melty the same way as before and took him home. Stitch then guarded Melty like a hawk in case Gantu decided to come by, while Keoni paid Lilo a visit to cheer her up, and everything turned out better than they had expected.
In the original and final timelines (in which Gantu slept peacefully and Reuben never informed him about the activated experiment), Melty was later found a one true place burning metal at the aluminum recycling plant.
In "Remmy", Melty was one of the experiments in Lilo's dream.
The first 624 experiments, including Melty, 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.
Melty participated in the following battle between the experiments and the Leroy clones by shooting attacking Leroys with blue energy blasts.
However, 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.
- Melty greatly resembles Mushu from Mulan in appearance, color, and that they are both dragons. However, unlike Melty, Mushu lacks wings and cannot fly.
- Melty's pod color is green.
- Melty is described by the experiment computer screen as, "Experiment 228. Primary function: Liquefaction of enemy fortresses, weaponry and transportation."
- Melty's body, ears, wings and tail appear in the online game Jumba's Lab.