Checkers

Checkers, A.K.A. Experiment 029, is an illegal genetic experiment created by Jumba Jookiba. He is designed to make his wearer a supreme ruler by hypnotizing those around them to honor them as if they were king or queen; his effects vanish as soon as he leaves his wearer's head, and other experiments are immune to his hypnotic effect. His one true place is as a decorative crown for certain festivals.

Personality
Checkers hasn't shown much emotion or individuality, other than once while running from Gantu. He mostly attaches himself to a person and stays there, almost as an inanimate object; however, on the head of Penny, he ate some of her sandwich and a hot pepper.

Lilo & Stitch: The Series
Experiment 029 was the 29th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to make his wearer a king or queen by hypnotizing those around them to worship them as royalty. 029 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.

Experiment 029 was activated off-screen and chased through Kokaua Town by Gantu before being rescued by Lilo and Stitch and taken home.

When Lilo discovered 029's powers, she, after naming him Checkers, donned him, thus becoming a queen. She then started bossing Nani and other people around, and made Mertle and the hula girls her bodyguards.

Before long, Mertle and the hula girls began arresting many people for defying their queen (including Pleakley), so Lilo decided to step down by removing Checkers. However, before she could figure out his one true place, Gantu arrived and grabbed Checkers. After putting the latter on his head, thus becoming a king, Gantu made his victims his servants.

Luckily, Stitch and Experiment 625 were immune to Checkers' hypnotic effect, and both cousins plotted to overthrow Gantu (who attempted to kill Jimmy, Reuben's pet cockroach, prior to Checkers' activation).

Later, Stitch and Reuben rallied an army of other experiments who, using their powers, rebelled against Gantu, and were able to remove Checkers from his head. As a result, Gantu's ex-servants revolted against him and kicked him out. Afterwards, Lilo and Stitch searched for Checkers' one true place.

In the end, Nani presumably wore Checkers during the Coconut Queen Festival while riding on a traditional parade float that Lilo, the hula girls, and Stitch's cousins had modified earlier.

The Origin of Stitch
Checkers was one of the experiments that was gliding on the screen, but he is 553 instead of 029.

Leroy & Stitch
The first 624 experiments, including Checkers, 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.

Checkers participated in the following battle between the experiments 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
Checkers has appeared on multiple occasions in the Stitch! anime wreaking havoc. It is also revealed that he will jump off of his host if he eats intolerably spicy food.

In "Princess Penny", Reuben used Checkers to temporarily rule over Gantu and Hämsterviel before taking him on a shopping trip and asking Stitch and Yuna to watch him while he bought some supplies.

Checkers reappears in "King Meega", intended to be used by Hämsterviel to command the inhabitants to capture Stitch, but escapes on his own to Yuna's school, where everyone intended to use his powers for themselves. Stitch had once captured Checkers and wore him on his head, but his hypnotic powers did not work on anyone else. Jumba recalls that Checkers' powers do not work with Stitch, since Stitch himself is immune to its effects. (This actually contradicts what happened in "Princess Penny", as Reuben had used Checkers himself without any problems.)

Trivia

 * Checkers will immediately jump off his host if he eats spicy food.
 * Checkers is also shown to be ticklish.
 * Checkers' pod color is yellow.
 * Checkers is described by the experiment computer screen as, "Experiment 029. Primary function: King maker. Give each wear the power of command in all living creatures."