Vivi is a Final Fantasy character that makes his debut in Kingdom Hearts II. He originates from Final Fantasy IX and is the only character from said game to appear in the series, although he is more weak-willed here. He is one of Seifer's gang's members, and the only member not from Final Fantasy VIII.
 Kingdom Hearts II
In the simulated Twilight Town, Vivi enters the Struggle competition. His data soon becomes possessed by a Nobody and he gains incredible powers. He easily defeats Seifer with his fast movement and speed and Roxas must battle him. After he is defeated, time will freeze and Vivi's data will reveal its true form to be a Dusk. After the Dusk is defeated, the real Vivi appears, wondering how he got here. Roxas later fights fourteen Vivis (created by Nobodies hacking the system) in a tunnel. The "real" Vivi appears, and after Roxas and company move away from the tunnel, it reveals its true form to be a Dusk. After that, Vivi will be seen with Seifer for the rest of the game.
Unlike the rest of Seifer's group, Vivi doesn't dislike Roxas and the others and is even quite friendly to them, always speaking in a polite tone and even offering Roxas his Struggle club when he was done training, although it is revealed that when Vivi does this he is actually a Nobody in disguise.
In the real Twilight Town, Vivi is often seen in the woods. He is the one that informs Sora that Seifer is attacked by Nobodies.
The oddity of his Struggle battle (such as his enlarging his Struggle Bat) may be a homage to the Black Magic that he uses in Final Fantasy IX. Furthermore, that Nobodies masquerade as him is a reference to his original Final Fantasy incarnation: in Final Fantasy IX, Black Mages were a race of magical beings created from Mist that did not possess souls. Thus most of them only lived a year before their bodies slowly shut down, but as the prototype Black Mage, Vivi had a much higher life expectancy. However, the truth of his origins still left Vivi questioning his existence and purpose in life. Various aspects of the Black Mage race are similar to the Nobodies of Kingdom Hearts.
Vivi in Kingdom Hearts II sports several minor changes to his appearance from his original design in Final Fantasy IX. His large, tan hat sports the most notable change. While in Final Fantasy IX the hat was normal, if oversized and a bit tattered, in Kingdom Hearts II the tip flops over and curls, what was once a large stitch has been replaced with an open zipper resembling a mouth in the middle of the hat, and two "eyes" just above this, shaped like a pale green star on the left and another, oblong shape on the right. He wears a sky blue coat with fancy, dark blue lining, secured by a tan string tied in a more complex manner than his original incarnation's. The white cuffs of this jacket are over-sized and sport similar lining to the rest of the jacket, though brown instead of blue.
The sleeves cover half of his hands, which are themselves covered by brown gloves. Vivi's jacket also has two large pockets on the front, each kept closed by a vertical white strap connected to a sky blue button. Vivi's face and body, partially visible under his jacket, is pitch black, albeit he looks more "solid" than he did in Final Fantasy IX, and his oval eyes are almost glowing yellow. His pants are green and held up by a brown belt, though in Final Fantasy IX the pants had alternating vertical stripes of green and white. On the reverse of this, Vivi's shoes in Final Fantasy IX were plain brown ones, but gain several tan stripes in Kingdom Hearts II.
In battle he can use many techniques: he can use his club to hammer down on his opponent with lightning speed, he can magically float in the air, he can use "Haste", where he does three very fast rising magic attacks, and finally he can cast "Flare" where he enlarges his club and does many spinning hits with his club that ends with a powerful magic blast.
Vivi Ornitier was one of the main protagonists of Final Fantasy IX, the final main game in the series to be released for the original PlayStation. He is one of many mass-produced Black Mages created by the main antagonist, Kuja. Most of Vivi's conflicts come from his own lack of self-belief, fearing his own powers and easily being led astray by lies. However, the one thing that haunts him the most is his real identity, often questioning his own existence as his race initially appears to be soulless with a fatally short life expectancy.