Amnesio

Amnesio, A.K.A. Experiment 303, is an illegal genetic experiment created by Jumba Jookiba. He is designed to wipe the memories of anyone he zaps in the eyes with the rays from his own; only a certain password, if spoken within earshot of him, reverses the process for all of those affected. He was captured by Gantu, but was rescued in "Snafu". His one true place is helping people with memory problems. Amnesio is voiced by Tress MacNeille.

Bio
Experiment 303 was the 303rd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to wipe 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.

Lilo & Stitch: The Series
303's pod was used as a ping-pong ball until it was 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 and activated 303, named Amnesio.

Amnesio went on to start wiping people's memories until he was discovered by Gantu. However, Gantu was unable to catch Amnesio because he was airborne, and managed to successfully evade all of Gantu's plasma blasts.

Gantu and Amnesio's presence captured the attention of Lilo and Stitch. Grabbing a butterfly net, Stitch climbed a telephone pole to try to catch Amnesio, but the latter sat on the telephone wire and was captured by Gantu in a containment orb. Before long, Lilo, Stitch and Gantu were fighting over the orb containing Amnesio, which ended with Amnesio wiping all three of their memories.

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 explaining 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 had discovered how to reverse Amnesio's effects, Gantu set Amnesio free. Lilo was devastated, even though Gantu said that he didn't want his memory back.

Fortunately, Stitch used his telescopic vision to track Amnesio, who headed into a factory. After a long chase, Lilo managed to undo Amnesio's effects by yelling out, "Ohana!" Although everyone got their memories back, Gantu was able to capture Amnesio and take off with him.

Amnesio was successfully sent to Hämsterviel, but the former ended up wiping Hämsterviel's memory also. Gantu misleadingly told Hämsterviel that he was a dangerous criminal who was 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 failsafe.

Stitch! anime
Amnesio made an appearance in the Stitch! anime where he used his powers on Stitch, Jumba, Gantu, Hämsterviel and Reuben. 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, their memories will be fully restored. Only Amnesio knows whose pouch belongs to whom. Not only that, it is shown that when Amnesio's powers are used on Stitch, he returns to his original programming since he is nothing but instinct in that state.

Trivia

 * The password which reverses Amnesio's memory-deleting powers is "ohana," a word which Jumba did not know of until well after Amnesio's creation.
 * 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 game Jumba's Lab.