Stewie Griffon

Stewie is extremely intelligent and speaks with an affected English accent. His Machiavellian ambitions not only include world domination, but matricide. In the commentary of one episode, MacFarlane reveals that Stewie's evil personality is a result of Lois smoking marijuana while pregnant with him. Lois also mentions this to Stewie in a dream of hers in "Mr. Griffin Goes to Washington."

Stewie has a sophisticated style, attitude and mannerisms, juxtaposed with typical childish interests. He enjoys literature such as Marlowe's Faust, Machiavelli, and Sun-Tzu (the latter two he read for advice on world domination). He cites pop culture references that date much farther back than his age would permit; however he has also shown an affinity for children's singer Raffi and has a hypnotic attraction to the Teletubbies. Stewie also succumbs to other failings of children his age: in "Emission Impossible", Lois subdues Stewie by blowing on his stomach. At one point Peter convinces Stewie that he has vanished into thin air by playing peek-a-boo with him. MacFarlane has stated that Stewie is meant to represent the general helplessness of an infant through the eyes of an adult. Consequently, his longing to conquer the world is based upon his desire for control over his own life.

Stewie is a scientific genius, apparently able to master physics and mechanical engineering, as well as construct a bewildering variety of machines including lasers, advanced fighter-jets, mind control devices, weather-control devices, robots, and even time machines. He frequently uses these devices to cope with the stresses of infant life (such as the pain from teething and his hatred of broccoli), to kill Lois, or for other purposes, such as destroying all of the sperm in Peter's body so he will not have to compete with another baby.

He has a complicated love-hate relationship with his mother. Even as he grudgingly acknowledges his dependence upon her, he reasons that matricide will free him of his present circumstances, which he finds intolerable. He often fantasizes of a world without Lois (in "Emission Impossible", he imagines her as a floor rug.) Stewie knows that because he is a toddler he would never be suspected should he successfully kill Lois; however this also means no adults take his plots seriously, and, to his constant vexation, Lois remains blissfully dismissive of his repeated attempts on her life. Stewie fails to realize that, if he did indeed kill Lois he would likely end up in foster care as revealed in "Petarded" when a judge rules the only reason the children can still live with Peter is because of Lois' presence. He does, however, suffer from a drug-like addiction to Lois' breast milk. In the episode "Stewie Loves Lois", after Lois fixes Rupert (his teddy bear) after a dog rips him apart, Stewie becomes enamored with her, up to the point where he drives Lois into having homicidal thoughts about her baby.

In general, Stewie has a strange relationship with both his parents. He almost never refers to his parents as "Mommy" or "Daddy", preferring to use the terms "Lois" and "The Fat one". In one early episode when Peter accidentally does a favor for Stewie, he thanks Peter by assuring him that "When the world is mine, your death will be quick and painless." In the episode 'The Courtship of Stewie's Father', the boys bond, though Stewie's subsequent behavior towards Peter appears no different than it was earlier in the series.

He also has a love-hate relationship with Brian; while he often jeers at him and seeks to undermine and mock him at every turn, he seems to find a grudging affinity with him, possibly because he is the only other intellectual in the family. Stewie's attraction to Brian may go yet deeper: when the two kiss incognito during the episode Deep Throats, Stewie seems to fall for the dog, saying 'Hey listen, freakin' shot in the dark: you wanna do something sometime?', and at one point calls Brian 'sexy', while drunk (Stewie Griffin: The Untold Story). In another episode, he asks Brian to spit on him in a SDM thing during a heat wave. The two even go on Hope-Crosby-like adventures, complete with musical numbers.