Amnesio

Amnesio, A.K.A. Experiment 303, is an illegal genetic experiment created by Jumba Jookiba. He is designed to wipe people's memories by zapping anyone hit in the eyes with the rays from his own; only a certain password spoken within earshot of him can reverse the process. He was captured by Gantu, but was rescued in "Snafu". His one true place is helping people with memory problems.

Lilo & Stitch: The Series
Experiment 303 was the 303rd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to erase his victims' memories. 303 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.

303's pod was used as a ping-pong ball by Keoni and another player until it got whacked off the table and into a little boy's bucket of sand. Thinking the pod was a marble, the boy put it on top of his sand castle. A small wave then splashed over the castle, activating 303, named Amnesio, whose existence scared the boy away.

Amnesio then left the beach and proceeded to start wiping everyone's memories until he was discovered by Gantu, who came for the experiment. However, Gantu had trouble catching Amnesio while the latter was airborne, as he managed to evade all of Gantu's plasma blasts.

Gantu and Amnesio's presence captured the attention of Lilo and Stitch, the former upset considering it was her birthday. Grabbing a butterfly net, Stitch climbed up a telephone pole to try to catch Amnesio, but after the latter perched atop a power line, he was captured in a containment orb by Gantu. Eventually, Lilo, Stitch and Gantu were fighting over the orb containing Amnesio, which ended with Amnesio erasing all three of their memories, leaving the trio dazed.

Plagued with amnesia, Lilo and Gantu decided to team up and figure out what to do with the captured experiment. Stitch, however, reverted to his original programming.

Lilo and Gantu (dubbed Martha and Lenny) later ran into Jumba and Pleakley, where Amnesio wiped both of their memories, but not before they explained to Lilo and Gantu exactly who was on whose team.

Lilo and Stitch then decided to team up to get their memories back. Lilo wanted Gantu to come with them, but the latter was unsure of himself. After Lilo discovered how to reverse Amnesio's effects, Gantu set the experiment free. Lilo was devastated, even though Gantu stated that he didn't want his memory back.

Fortunately, Stitch used his telescopic vision to track Amnesio, and Lilo, Stitch and Gantu chased him into a factory. Amnesio's effects were later undone by Lilo yelling out, "ʻOhana!" Although everyone got their memories back, Gantu ultimately managed to recapture Amnesio in a container and take off with him.

Amnesio was successfully sent to an impatient Hämsterviel, but the former ended up erasing Hämsterviel's memory also. Gantu misleadingly told Hämsterviel that he was a dangerous criminal who had been captured by him, Ace Jackson, while looking at a jar that read "World's Greatest Cop," which Lilo had made Gantu earlier.

Amnesio 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
In the film's opening, Amnesio can be seen waving hello to Lilo, along with Snooty and Babyfier.

Later, the first 624 experiments, including Amnesio, 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.

Amnesio participated in the following battle between the experiments and the Leroy clones by erasing Leroys' memories.

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 `Oe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.

Stitch! anime
Amnesio made an appearance in the Stitch! anime where he used his powers on BooGoo, Stitch, Jumba, Gantu, Reuben and Hämsterviel. It is revealed that Amnesio holds the stored memories in pouches under his wings. If his victims ingest the pouch with their memories in it, everyone's memory will be fully restored. Only Amnesio knows whose pouch belongs to whom. Also, it is shown that when Amnesio's powers are used on Stitch, he reverts to his original programming since he is nothing but instinct in that state.

Trivia

 * When Amnesio flies around in several instances of his episode, the song "Flight of the Bumblebee" plays.
 * The password which reverses Amnesio's memory-deleting powers is "ʻohana," a word which Jumba did not know of until well after Amnesio's creation.
 * The password could possibly be "family," but it works in any language.
 * Amnesio's pod color is yellow.
 * Amnesio is described by the experiment computer screen as, "Experiment 303. Primary function: Erases memories."
 * Amnesio's head appears in the online game Jumba's Lab.