Katsura

Blaine was a former member of Team Rocket, joining because of his interest in science, conducting experiments on some of Red's future Pokémon, namely Gyarados and Eevee. But after hearing of Red's clashes with Team Rocket, like protecting Mew from Team Rocket, Blaine left, attempting to make up for his evil deeds. When Red reached Cinnabar Island, Blaine was under attack by members of Team Rocket and their newly captured Moltres, on loan from Sabrina.

Blaine had his Rapidash carry Red to his Pokémon Lab, who in return let Blaine use his Gyarados to hold off Moltres, where Red was able to revive an Aerodactyl from a fossil. Aerodactyl helped rescue Blaine and defeat Moltres.

Later, Blaine asked Red to help him in Cerulean Cave. While he was working under Team Rocket, Blaine combined some of Mew's DNA with his own to create a hybrid Pokémon named Mewtwo. Some of Blaine's hand was infected with Mewtwo's DNA, and thus he was able to track the synthetic Pokémon. Because of this, Team Rocket attempted to abduct Blaine to review Mewtwo's whereabouts. Using the Master Ball, Red was able to capture Mewtwo for Blaine.

The psychic bond between Mewtwo and Blaine limited them both. If they were apart for too long, both would begin to become ill. Blaine worked for several years trying to find a way to sever the bond without hurting either of them.

During the Cerise Island incident, Sabrina's Spoons of Destiny paired Blaine and Yellow together in the fight against the Elite Four. Together, they confronted Lance. However, the bond between Mewtwo and Blaine proved to be their undoing, and they were defeated, leaving Yellow to face Lance alone.

Later, during the Mask of Ice's plot in Johto, Entei chose Blaine to be its partner. The healing power of Entei's flames was finally able to cut the link between Mewtwo and Blaine, and the two were free to live their lives apart from each other.

Although he's serious for most situations, he also had his comical moments like getting his moustache burnt when he was training and had to use fake ones. Sometimes he may also use riddles to lighten up dark atmosphere.

(Source: Bulbapedia)