Ace

Ace, A.K.A. Experiment 262, is an illegal genetic experiment created by Jumba Jookiba. He is a failed experiment that has no evil function. Instead, he is pure good, and to top it off, he is the only experiment programmed not to cause trouble. His one true place was originally as a member of AARG, balancing out Jumba's evil, and as a local do-gooder, but his actions have promoted him to a worldwide superhero.

Personality
Ace appears as the exact equivalent of Experiment 627, as he will do virtually any good deed for the sake of being good, due to the glitch in his program. Ace is a slight show-off, striking heroic poses for fans after saving the day, and his heroic actions have caused him to become a worldwide superhero.

Lilo & Stitch: The Series
Experiment 262 was the 262nd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to be a pure evil experiment, but was instead a pure good superhero, much to Jumba's embarrassment. According to Reuben, Jumba kept 262 locked in the basement when friends came over. 262 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 262's pod landing in a bush by a house.

Prior to the events of 262, Jumba heard from the head of E.G.O. (Evil Genius Organization), who threatened to revoke Jumba's membership, believing the latter had reformed. However, Lilo and Stitch convinced the alien chief to visit Earth so they could prove to him that Jumba was still worthy of membership.

When the head of E.G.O. arrived at the Pelekai household, Lilo and Stitch tried to trick him into thinking that Jumba was still evil by showcasing some of Jumba's evil experiments.

Later, when a fire started in another house, a fireman, while trying to put out the fire, accidentally drenched the nearby bush with water from his fire hose, activating 262.

Gantu had been informed about 262, but since the experiment had no evil uses, he didn't bother capturing it.

When 262 heard that the family's pet kitten was trapped inside the burning house, he heroically rushed in and rescued the feline from the fire by jumping out a window with the kitten, using a bedsheet as a parachute.

262, named Ace, then put out the fire using the fireman's hose, and found his one true place as a local do-gooder.

Meanwhile, Lilo and Stitch's facade was successful until the head of E.G.O. saw a screen of Ace rescuing the same kitten. As a result, the chief turned Jumba down and promptly left.

Leroy & Stitch
Ace was seen early in the movie as Lilo was making her rounds with Scrump to make sure all the experiments were happy in the one true place they belonged.

Later, the first 624 experiments, including Ace, 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.

Ace participated in the following battle between the experiment and the Leroy clones.

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
Ace made an appearance in a bonus episode of the Stitch! anime where he takes Stitch under his wing as a hero. It is revealed that Ace can now not only speak English and fly, but has also become a worldwide superhero. He helped re-energize Stitch after he was almost erased from existence, due to a time-traveling incident in which his creation was tampered with. He later appeared as one of the experiments who helped Stitch fight Dark End.

Trivia

 * Ace is one of the few experiments that was not evil before he was found by Lilo and Stitch.
 * Intriguingly, Ace's number is the opposite of Stitch's, and while Stitch was originally pure evil, Ace was always pure good.
 * Ace is also the polar opposite of 627 and Leroy, since Ace has no evil uses, whereas 627 and Leroy have no good uses and cannot be rehabilitated.
 * Ace's pod color is yellow.
 * Ace is described by the experiment computer screen as, "Experiment 262. Primary function: Error. Experiment classification failure. 262 has no known evil uses."
 * Ace is one of the few experiments to not appear in the group photo at the end of Leroy & Stitch.