Dumbo

Dumbo is a Summon character called forth by Sora in combat in Kingdom Hearts and Kingdom Hearts: Chain of Memories. He is originally from the Disney movie "Dumbo"

Kingdom Hearts
''A baby circus elephant. He was taunted because of his huge ears, but his talent for flying made him the star of the circus.''

''Ascend with button, descend with  button. Attack: Splash. Cost: 3 MP.''

He first flew onto the screen in "Dumbo" (1941).

Kingdom Hearts: Chain of Memories
A small elephant born in a circus.

The other animals laughed at his big ears, but the courage to fly made Dumbo the star of the circus.

If Sora calls, Dumbo will come to the rescue.

Kingdom Hearts
Apparently being the sole survivor of the destruction of his world, like several other summon characters, Dumbo's spirit survived in the form of the Watergleam Gem, which Sora discovered while trapped inside Monstro. Upon giving it to the Fairy Godmother in Traverse Town, she restores Dumbo's spirit and Sora learns his summon. After Xehanort's Heartless was defeated and Kingdom Hearts was sealed, Dumbo most likely returned to his world.

Kingdom Hearts: Chain of Memories
Dumbo is another character who is recreated from Sora's memories. He once again acts as a summon, and you can obtain his card after you complete the Monstro floor.

Abilities
When summoned, Dumbo hovers in midair with Sora riding on his back. The two are invulnerable to harm until Dumbo is dismissed or runs out of MP. Dumbo blasts a jet of water from his trunk at the enemies, drenching them, pushing them backwards or defeating them. Dumbo can also ascend and descend in flight. Dumbo is a useful Summon and is best used when surrounded by Heartless. When Sora summons Dumbo in Neverland, Dumbo is able to fly freely in the air instead of just hovering around.

Trivia

 * In Re:CoM, Dumbo is one of the only Summons that makes Sora leave the battlefield; the other is Cloud.