Chicken Little is a Summon obtainable through the Baseball Charm. This is unlocked after being summoned to Hollow Bastion, after you get back Pooh's book from the Heartless and discover that the pages have been stolen. After notifying Merlin of this, he will give you the Baseball Charm.
 Journal Entries
 Kingdom Hearts II
Chicken Little (2005)
Chicken Little has more pluck and heart than most boys twice his size. He never turns away from a challenge, no matter how big it is.
He's a loyal pal of Sora's, and is always quick to answer a call for help.