-Maximillion Pegasus-
He owns many cards that have never been released to the public. He originally wanted to be an artist before becoming obsessed with Egypt and creating Duel Monsters. This did serve to fulfill his original dream as he drew monsters for his game. He wants to take over KaibaCorp and gain possession of the Millennium Items to combine KaibaCorp technology with the items in the hope of reviving his lover, Cecelia.
-Personality-
Pegasus is depicted as a well-mannered yet overly dramatic man obsessed with cartoons, concealing the appearance of a ruthless businessman and gamer, and yet a man of his word.
Pegasus has a habit of calling Yugi "Yugi-boy" and Kaiba "Kaiba-boy". When sufficiently provoked, he can have a temper. Pegasus is also notable for his foppish manner, dandified appearance, and effeminate hairstyle, all of which have led to him being referred to as "cutie-pie" (by Bandit Keith) and an "overdressed prima donna" (by Joey Wheeler).
Pegasus is interested in cartoons, especially Funny Bunny, which he watched every Saturday morning while growing up in America. Cartoons are the inspiration for many of his cards, such as the toon monsters.
Pegasus at first comes across as a cheater with a thirst for collecting souls and achieving his ambitions. This impression is changed when his true motive is revealed. Not only is Pegasus an excellent businessman, his motivations for acting as the above was the resurrection of his deceased lover Cecelia. Because he needed KaibaCorp's Solid Vision and thus needed KaibaCorp, the deal with the Big Five is that he be given control if he beat Yugi, to restore Kaiba Corp's reputation as Yugi beat Kaiba. From this, his cheating to beat Yugi and kidnapping Solomon, Mokuba, and Seto Kaiba becomes somewhat understandable. Furthermore, Pegasus himself honors his pledge to Yugi Muto claiming to be both "duty-bound" and a "man of [his] word", releasing the souls of Solomon Muto, Seto and, Mokuba Kaiba before being defeated in a Shadow Game by Yami Bakura.
Despite cheating with the Millennium Eye himself, Pegasus showed a dislike for people who cheat for personal gain, such as Bandit Keith (who cheated right in front of him). In the anime, he was somewhat light-hearted in this aspect, simply making fun of Keith while dropping him with a trapdoor. However, he allowed the Duel to continue, presumably to see how Joey had grown as a Duelist.
Pegasus often puts on a timid facade to trick his enemies. He pretends to be discouraged by minor upsets in his duels with Yugi and Kaiba, then acts as if his strategies are purely luck-based. When Kaiba attempts to use the duel disk prototypes, Pegasus pretends that he's too weak to carry the device, forcing Kaiba to use Pegasus' arena.
Years later, Pegasus dropped his ruthless facade completely and became more laid back and jovial. This was shown during his Duel against Vellian Crowler and Jean-Louis Bonaparte.
-Voice and mannerisms-
Being an American, Pegasus has a tendency to use English words when speaking in the Japanese version. He also has a somewhat poor grasp of the Japanese language itself, repeatedly using the word "desu" (です, meaning "is") in places where it has no meaning.