Wakka is a resident of the Destiny Islands and a friend of Sora, Kairi, and Riku. He spends a lot of time with Tidus and Selphie, and treats them just as a big brother would. He and Tidus expressed their curiosity over the Secret Place, and were thinking of exploring it.
Like Selphie and Tidus, Wakka appears in Sora's Dive to the Heart on the Destiny Islands area. His question, "What do you want outta life?" also helps determine the leveling pace throughout the rest of the game. Sora can answer with either A) to see rare sights, B) to broaden my horizons, or C) to be strong.
He can be fought while on Destiny Islands. He uses his Blitzball to attack as he did in Final Fantasy X (thus requiring the player to deflect Wakka's Blitzball back at him), but this one lacking the bumps and Spiran script for the word "Blitzball" of the original Blitzball. Nevertheless, this makes him, out of all the Destiny Islands and Twilight Town Final Fantasy characters, the only one to use exactly the same weapon as his original incarnation.
After Destiny Islands is destroyed, it is unknown what happened to him.
A memory-based version of Wakka appears in Kingdom Hearts: Chain of Memories inside the Destiny Islands simulation in Castle Oblivion. In the ending credits of Kingdom Hearts Re:Chain of Memories, the real Wakka is shown playing with Selphie and Tidus on a beach while Kairi is facing the Small Island.
Wakka makes no appearance in Kingdom Hearts II, just as Tidus doesn't. The two are only briefly mentioned by Selphie when she is talking to Kairi early on in the game, described as being "wrapped up in their ball game." (A reference to Blitzball from Final Fantasy X.)
Wakka makes his third appearance in Kingdom Hearts coded, this time as a data version of himself, appearing on the data version of Destiny Islands, alongside Tidus and Selphie. He appears on Destiny Islands talking to Sora.
Wakka in Kingdom Hearts resembles his Final Fantasy X incarnation, but is younger and sports a simpler outfit. Wakka retains his orange hair and enormous coif, as well as his baggy yellow pants that close up halfway down his lower legs. Each leg of these pants has a large, grey, "X"-shaped strap with blue tips, possibly referencing Wakka's game of origin. In Final Fantasy X, these "X"s were located on Wakka's jacket, while his pant legs sported three straps on each leg shaped like thinner "X"s. Wakka wears a tank top resembling his original jacket, though the jacket was mostly orange and black, as opposed to this tank top's pale yellow color with black lining. Like in his original game, he wears sandals, though this Wakka's sandals are green. He wears blue wristbands on each wrist, has brown eyes, and has small stud earrings not present in his original design. Wakka lacks the fish necklace he wore in Final Fantasy X, and wields a simpler version of his Blitzball as a weapon.
Like in Final Fantasy X, Wakka fights by throwing his Blitzball.
On Destiny Islands, he practices fighting skills with Sora as a way for the player to improve his level. During this battle, if Sora can manage to block one of Wakka's attacks via hitting the ball back at him, it earns him one tech point. If Wakka jumps in the air and throws the ball at Sora and Sora successfully blocks it he gets two tech points. After defeating Tidus, Selphie, and Wakka as individuals, Sora is able to fight against them all at the same time.
Like Selphie and Tidus, Wakka's battle stance and basic attack are based off his Final Fantasy X appearance. Also, his attack where he yells "Take this!" is based off one of his Overdrives, Status Reels.
In Final Fantasy X, Wakka is a major character and a twenty-three year old professional blitzball player. He uses blitzballs as his weapons in battle, similar to his Kingdom Hearts counterpart. Throughout the game, Wakka forms a close brotherly relationship with Tidus.