Stitch

In Kingdom Hearts II, Stitch is a summon made available by opening a chest in Hollow Bastion after the first visit to Space Paranoids. Only Stitch's Earth form is seen and his abilities comprise of his blasters and ukulele, as opposed to his true form (four arms total, antennae and hair-like spines on his back) and his powers as Experiment #626. How he arrived to Hollow Bastion and whether or not his unnamed world was destroyed is unknown.

Kingdom Hearts II
Lilo and Stitch (2002)

A strange visitor from a distant planet.

Stitch is very strong for his small size and prone to mischief.

He's always ready to help his friend Sora whenever Sora needs him.

Role
Stitch is one of two summons during Kingdom Hearts II that makes a difference to the storyline. His first appearance was when Sora, Donald and Goofy went into the corridors leading to Ansem's study; he was seen crawling above them without their notice. During the next cutscene, he droped down onto the keyboard of the computer. Donald jumped onto the keyboard to grab him, but Stitch jumped off. As Donald turned around, he mashes the keys, causing the MCP to be alerted.

Later, in a cutscene showing the Final Fantasy characters fighting Heartless in the The Great Maw, Stitch was seen fighting alongside them. His weapons in the cutscene are his blasters from Lilo & Stitch.

Summon
Using the Ukelele Charm, Stitch can be summoned in a battle. Stitch is unique as a summon because he does not actually enter the field when summoned; he instead jumps and crawls around the HUD features. After the summoning scene, Sora tries to follow him, but comically hits the TV screen and returns to gameplay. Stitch stays on the HUD and does most of his actions from there. Usually he will shoot at enemies from the Command menu, or will crawl over to the HP and MP bars and replenish them by erratically licking them. Occasionally, Stitch will also play his ukulele to damage some enemies.

His Limit attack is Ohana, in which Sora uses the Keyblade as a guitar while Stitch also plays on a ukulele.

Trivia

 * In Lilo & Stitch, Stitch traveled on a space ship to Earth. Many speculate that, like the movie, Stitch is not a native of Radiant Garden; rather, he's a visitor via gummi ship.