Tidus

Tidus is a minor character in the Kingdom Hearts series, originally from Final Fantasy X.

Kingdom Hearts
''A cheerful, self-confident boy who lived on the Destiny Islands. He considers himself a champ at everything. Nobody knows what happened to him after his island disappeared. "Final Fantasy X"''

Kingdom Hearts
Tidus is a friend of Sora, Riku, and Kairi, and is a resident of the Destiny Islands, spending most of his time with Wakka and Selphie.

If Sora loses a practice battle with Tidus on the second day in the Destiny Islands, Tidus performs his victory pose from Final Fantasy X, namely, tossing his sword upward then catching it before swinging it to his side.

Kingdom Hearts: Chain of Memories
In Kingdom Hearts: Chain of Memories, Tidus appears with Wakka and Selphie in both Sora and Riku's stories as part of the memory-based Destiny Islands in Castle Oblivion.

Kingdom Hearts II
He does not appear in Kingdom Hearts II, but Selphie mentions that he and Wakka are "All wrapped up in their ball game," which anyone who has played Final Fantasy X should recognize as blitzball.

Unlike the original Kingdom Hearts, which pronounced his name with a hard E sound, when Selphie mentions him in Kingdom Hearts II, she says his name with a hard I sound instead.

Trivia
When "Another Side, Another Story" was first seen, Roxas (also known as Blonde-Haired Kid) was speculated to be Tidus.