Stewart "Stewie" Gilligan Griffin is the flamboyant and eccentric one year old infant of Peter and Lois Griffin. Stewie, equipped with his teddy bear, Rupert and his laser gun, has, on several occasions, almost single handedly taken over the world and he seems to be obsessed with world domination and matricide. In The Real Live Griffins, he was played by Ashley Olsen. Although he has remained physically one year old since "Chitty Chitty Death Bang", mentally he seems much older, even proclaiming in "I Never Met the Dead Man" to be shooting on a fifth grade level.
Stewie is well-spoken, with an advanced vocabulary, an upper-class British accent and an ambiguous sexual orientation. He refers to Peter often as 'The Fat man' and his mother by her given name, Lois. Seth MacFarlane has described him as "an evil Rex Harrison". Stewie is constantly plotting ways to kill his mother, Lois, apparently holding a grudge against her because of his nine-month stay in her "ovarian Bastille." He shares his secrets with his confidant and teddy bear Rupert. Stewie often speaks from the standpoint of a much older person, saying such things as "What is it that you children are into nowadays?"
On the show, Stewie engages in extreme violent or criminal acts, including robbery, carjacking, loan sharking, forgery, and killing off many minor characters. The characters he kills off are for reasons such as anger, jealousy, and grudges he holds. Stewie's mastery of physics, mechanical engineering, and firearms are at a level of science fiction. He has constructed advanced fighter-jets, a mind control device, a weather control device, robots, a time machine, a shrinking pod, a teleportation device, and more. Stewie employs these to deal with the stresses of infant life such as teething pain, and his hatred of broccoli or to kill his mother. Stewie also shows infant-like tendencies such as pretending his tryke is an actual vehicle. Stewie's ability to move objects of greater weight than himself is not surprising to other characters, nor is his ability to perform martial arts or retrieve firearms from hammerspace. In "Dog Gone", after he made jokes about Brian killing a dog, Brian asks him how he'd feel if he had killed another baby. He merely replied by telling him he's killed seven, acting as if it was no big deal. He also tries to get children to drink poison. In "Love Thy Trophy" his foster siblings who are each of different races asked him if he wanted to lay down and complete their people rainbow and he suggested that they play "Drink the Stuff Under the Sink" instead. In "Emission Impossible" he went to Lois in his Peter Bot and told Chris and Meg to drink the anti freeze in the garage.
Stewie, like his mother, has a masochistic personality. This was revealed in "Peter's Two Dads" when Lois spanked Stewie for destroying her pearl necklace. Stewie later confided to Rupert that he found that he enjoyed suffering from such pain, and unsuccessfully went out of his way to provoke Lois several times in the episode into spanking him again. He even had a day dream in which he was tortured by Lois, who was clad in a dominatrix outfit. In "Be Careful What You Fish For", Stewie comes home with his right arm pulled out of its socket, Brian then stuffs Stewie's mouth with paper so he can't yell for Lois. Brian then painfully but successfully puts Stewie's arm back in its socket. After the act, Stewie notes that he won't say if he liked it or not. In "Friends of Peter G", shown in a vision given by Death, Peter enters the kitchen drunk and angry, forcing his family to line up to get cigar burns. After Stewie is burned, he returns in a disguise in hopes to get burned again. In "Total Recall", he claims he plays choking games with Rupert.
Early in the series he was portrayed as being completely obsessed with world domination and killing Lois. In "Chitty Chitty Death Bang", It was revealed that after Stewie's birth, the doctor found a map of Europe with plans to bomb its capitals inside Lois. In "Stewie Loves Lois", Stewie's favorite meal is cut green beans, Atkins friendly potato sticks arranged in order of size, from large to small, and a Scooby-Doo yogurt with Shaggy's eyes scratched out. He still wants to kill Lois and take over the world but those traits have taken a back seat, although in select episodes Stewie has exhibited some of his more sociopathic traits, such as aggressively shooting Brian in the leg in "Back to the Pilot". Stewie tried to recapture some of those traits in "The Hand That Rocks the Wheelchair" and ended up creating an evil clone of himself.
Despite all of Stewie's evil traits he did genuinely care about Brian. In "Brian & Stewie" he revealed that he considered Brian to be his only friend and the only person in the entire world that he cared about. When ordered to kill Brian by his girlfriend Penelope in "Mr. and Mrs. Stewie", Stewie struggled to do so but eventually chose to spare Brian and protect him from Penelope. He also comforted Brian after Glenn Quagmire ranted about how much he hated him in "Jerome Is the New Black" and informed Brian that he didn't need Quagmire to like him as long as he liked himself. He then added that he liked him and allowed him to sleep in his room.
When Brian was killed by a car in "Life of Brian", Stewie's devastation over Brian's death caused him to be cold and nasty towards Vinny, a replacement family dog until Vinny told him that he understood what he was going through due to the death of his own previous owner. After that, Stewie bonded with Vinny, imitating his Italian personality at times such as in "In Harmony's Way" when Vinny suggests Quagmire wear a necklace.
A running gag has occurred over whether or not the family can understand Stewie's speech, especially given his tendency towards homicidal remarks. The Griffins appear to ignore most of what Stewie says, though on occasion they have responded to his speech.
This has been referred in "E. Peterbus Unum" as a meta-joke. The end of the episode reveals it actually being a historical video, projected to a group of students in the future. When the presenter asks if there are any questions, one of the students responds with "I don't get it. So.... like... can the family understand the baby or... what's the deal with that?" The other students are seen nodding in agreement with the apparent confusion.
Brian and Jillian are the only adults that seem to fully understand what he's saying; however there have been occasions when other characters have evidently understood him. Brian can always understand him though, and they often have conversations between themselves, including musical numbers, arguments and bad advice. Strangers such as Connie DiMico can also understand Stewie in "McStroke", as can Jillian. Lauren Conrad is even able to understand him. On the rare occasions he speaks directly to Meg or Chris they also sometimes reply.
In "Extra Large Medium", Chris has a lot of dialog with Stewie that make it plain that he is able to understand him.
"Stewie Kills Lois" and "Lois Kills Stewie" are the only episodes where he is really spoken to properly by all family members, but these two episodes were simulations but still had a strong possibility of happening. Stewie complained that they were only NOW interested in him since they had found out he was an evil genius, whereas the previous week Peter had ignored his macaroni picture of an owl.
During a dream in "Bigfat", Hank Hill walks in and demands to know who the fat guy is sleeping with his wife Lois, before waking up again with his real wife Peggy Hill and complains about not getting to find out if they can understand what Stewie says.
When the family adopted Vinny, he was able to understand Stewie perfectly and throughout all the episodes with him, Vinny and Stewie exchanged dialogue just like he does with Brian.
A mall Santa is able to understand Stewie in "Christmas Guy".
When being carried home from the hospital in "Yug Ylimaf", Chris questions if anyone else heard Stewie while he talked to Brian after being born. This is immediately dismissed by Lois.
When Peter discovers a whip in Quagmire's mail and decides to play with it in "Herpe, the Love Sore", Stewie compliments him on the "Cool hWhip" and Peter turns the whip on him as Stewie questions how Peter can suddenly understand him.
When Stewie comments to Chris that someone should call Lois a pig for picking her teeth at the table in "Meg Stinks!", Chris actually does it while Lois misses the comment from Stewie.
Both Meg and Chris conspire with Stewie to embarrass Brian over his predictable pretentiousness in "A Shot in the Dark".
He shows that he does not have a complete knowledge of sexual intercourse as shown in "Chick Cancer" where he says he thinks sex is "a kind of cake.", and once was horrified upon accidentally catching his parents in the act of lovemaking. Even by age 35 Stewie does not know how to have sex, although in Stewie Griffin: The Untold Story he changes the future after seeing it as a baby.
The Gay Side of Stewie
Stewie is seemingly a closet bisexual. Continuous jokes during the series involves Stewie and homosexuality. Stewie also has seem frequently flirting with male characters in the series.
Still, he has seemed attracted to female characters. The more realistic situations this is, whenever the character of Stewie interest involves is of his age involves girls. Some rare times Stewie showed repulse of homosexuality.
Also, in several occasions Stewie showed interest in Brian.
Stewie has some kind of romantic or sexual fantasy involving his stuffed toy, Rupert. Stewie sees him as an athletic man with a teddy bear's head. Stewie had several times referred to him as gay. In "Excellence in Broadcasting", Stewie accidentally discovers masturbation, and begins to fantasize about being tied to his crib while a muscular Brian and Rupert kiss.
In "Fifteen Minutes of Shame" he said that he didn't really like women and thought it would be interesting if it turned out he was gay.
In a canceled episode named "Queer Is Stewie?", he came out of the closet. This never saw the light of day due to the show's cancellation. The episode was later redone and expanded to have Stewie finding his future self.
Seth MacFarlane, the creator of Family Guy, has stated in an interview that "He originally began as this diabolical villain, but then we delved into the idea of his confused sexuality. We all feel that Stewie is almost certainly gay, and he’s in the process of figuring it out for himself. We haven’t ever really locked into it because we get a lot of good jokes from both sides, but we treat him oftentimes as if we were writing a gay character."
Stewie's side of his bisexual nature changes from episode to episode. For example, in "Movin' Out (Brian's Song)" he was gay, and in "Dammit Janet!" he is straight. Sometimes he shows signs of both in one episode like "Ocean's Three and a Half" and "Family Gay."
Seth MacFarlane has speculated that when Stewie grows up, he will ultimately become either a homosexual or a repressed, unhappy heterosexual. Seth would later retract that statement pointing out that being a cartoon character, can be neither straight nor gay.
In "The Thin White Line", Stewie sings to a ship full of sailors:
"Well, despite your point of view
I can thrill a girl or two-
But I'd rather get it on with you!"
Also there is a quote after escaping the cops, while dressed as a girl in "Boys Do Cry"
- Brian: How you holding up Stewie?
- Stewie: Umm, I feel right Brian, I feel right.
There is also a scene in "Deep Throats" that suggests he's attracted to Brian. He makes a similar drunken admission in Stewie Griffin: The Untold Story. In the same episode he asks Brian to shave his "coin purse".
He even tried to trick Brian into having sex with him, in "Movin' Out (Brian's Song)". He has also kissed Brian several times on the show. In "No Meals on Wheels", he is tricked by Brian into yelling "Yahtzee" and he does it in a feminine way. In "No Chris Left Behind" he says he hopes to join a group of gay men. In "The Tan Aquatic with Steve Zissou", Stewie had a panic about having cancer, and wanted to have his list of things to be done before he died to be completed. One of those things was to learn how to ballroom dance with Brian. In that part, Stewie dressed himself in a pink dress and ear-rings. After they have danced for a while, Stewie whispers, "I love you." to Brian. In "Love, Blactually", Stewie sucks his finger after "accidentally" putting it into Brian's mouth. In "420", Brian asks if Stewie can give him a sample of his pee to trick Joe, who wanted to use the sample to check if Brian was smoking marijuana. Stewie looks very happy to accomplish Brian's request, and even gets naked to do it. In "Peter Griffin: Husband, Father...Brother?" he and Brian were hypnotized into kissing each other, but doesn't remember even though he says he tasted crotch.
In "Saving Private Brian", he and Brian kiss to get kicked out of the army. Then while kissing another gay man who happens to be an officer comes up to them and says,
- Gay man: "Any room for one more?"
- Stewie: "Hell yeah!"
- Dylan: Stewie, why are you naked?
- Stewie: Oh, just a little something I do around here once a week called naked tea party. Got my teacup here, now all I need is a teabag. That something that interests you my friend?
- Dylan: You're weird.
- Stewie: And you're attractive; now take your fucking pants off!
In "We Love You, Conrad" Stewie, revealed his alter ego, Desiree. Showing that he had many boyfriends including one named Lee. In "Chick Cancer", during the ending credits, Stewie said that he could totally get into being gay. In "Not All Dogs Go To Heaven" he is asked if he is queer to which he replies "probably". In "Three Kings" Stewie takes the role of Annie Wilkes in which he shows strong sexual attraction to Brian who he fondled. In "Screwed the Pooch", he says he likes to go to disco themed gay bars to relax. Similar hints are given during other episodes. In "Family Gay", when he tells Brian about the straight camp, a place where gay people go to become straight, he shows him a folder about it. When Brian notices that it's dated last year, Stewie looks uncomfortable and says that it was just something that he found in the street.
In "FOX-y Lady" he eats a phallus-like banana and enjoys it.
In "Stewie Kills Lois" before he begins to board Peter and Lois's cruise ship, he says to Brian, "An hour from now I'll be surrounded by sea men (Semen). Sperm whales and sea men." He then notices a bird and says, "Oooh, a swallow."
In "Road to the Multiverse" Brian and Stewie arrive in a universe full of gays and he says "Love it". He also goes to a universe where everyone has two heads and it shows him kissing himself.
In "Ocean's Three and a Half" Stewie confesses his attraction to Brian Adams at the end.
Stewie has a horrified reaction to seeing the online video 2 girls, 1 cup in "Back to the Woods", but after the initial shock starts wondering if there is a video of two guys doing the same thing, eventually suggesting Brian to look it up.
In "Road to Germany", Stewie was flying a plane and made some odd gestures at a passing pilot. However when the pilot had his shirt off and was rubbing his nipple, Stewie looked stunned as if he had gone too far. Also, when asked what qualified him to fly, his response included a notation of being homosexual.
When Peter starts collecting horse sperm in "Family Gay", he warns the family that some refrigerator containers contain sperm instead of milk. Stewie stops for a moment and looks at his cereal, then slowly continues to eat.
In "Brian & Stewie", Stewie told Brian to lick his diaper clean and to lick his ass, and especially wanted Brian to lick his ass, and later admitted he loved him.
In "Death Lives", Lois ties Stewie to a flag pole, and while she was dragging him up, his bottom dragged against the side of the pole, at which he tells Lois to go slower and that he must do it again while no one was watching.
In "Baby Not On Board" he is horrified at the sight of a nude woman's vagina in a pornographic magazine, even seizing a machine gun, firing upon and obliterating the offending publication. Later in the episode he admits to disabling the parental lock on the TV and watching "so much porn."
In "Valentine's Day in Quahog", Lois comes down stairs to a dark living room. Believing it is Peter, she takes off her robe, asking if he is' 'ready for his Valentine's gift', she turns on the lights sees Stewie on the couch. He then responds that 'he is ready for therapy'. Later, Brian asserts that Stewie is more of a woman than all of his previous dates which Stewie assembled to confront him as to why their relationships failed.
The Straight Side of Stewie
There are also many references to him being straight, as seen in "Dammit Janet!", where he falls in love with a female toddler. Stewie is shown to hate gay people in some episodes like "Road to Rhode Island" where he asks why everyone comes out to him, and in "Mr. Griffin Goes to Washington" he says "not ass you pervert save it for the interns".
Stewie has twice had a relationship with another young toddler/beauty queen named Olivia. He also became sexually aroused while watching the female cheerleaders undress. Stewie also came close to having sex with Connie DiMico in "McStroke". In Stewie Griffin: The Untold Story, his older self had sex with a girl named Fran for 8 seconds - then cried for 40 minutes. Stewie also became furious when he discovered that his future self was a virgin. At first sight, Stewie was also instantly attracted to Jillian. He is also easily annoyed by Jasper, Brian's gay cousin. Stewie falls in love with his babysitter in "8 Simple Rules for Buying My Teenage Daughter". In "Breaking Out is Hard to Do" he complains that there was not a single female baby in Asiantown. Also, in "Ocean's Three and a Half", Stewie falls madly in love with Susie Swanson, the Swanson's new baby, and tries to impress her with a song but by the time the episode was over he had lost interest in her only to fall in love with Bryan Adams.
Stewie also has a running gag in the series where he throws "Sexy Parties" that involve many women in tight and revealing outfits. Overall, these scenes indicate that Stewie is clueless as for what "sexy" means, but rather imagines parties suited for toddlers: laughing, running around a-la-Benny Hill or playing Red Light, Green Light.
In "Mr. Saturday Knight", Stewie was at a funeral and was looking at all the girls and was counting which female babies he would "do" or "wouldn't do".
In "Blind Ambition", in a cutaway, he tries to check out female babies with his pimped up big wheel in the playground.
In "Family Gay" he quoted "Homosexuality is wrong".
He announces "BILF" (Baby I'd like to fuck) at the approach of a female infant in "And I'm Joyce Kinney".
Stewie falls for Penelope in "Mr. and Mrs. Stewie", believing he has found his soul mate. Despite a major fight over Brian, Stewie gets a kiss and a smile from Penelope after defeating her. He notes he will tell his friends he "banged" her.
In Valentine's Day in Quahog", Stewie falls for an infant Lois, but becomes violently ill after learning who she is.
None of the other Griffin family members have Stewie's uniquely shaped head. In "Stuck Together, Torn Apart", Stewie did have a head shape similar to Meg's until he was bouncing on the bed and hit the ceiling, thus flattening it into the familiar football shape. Also, in "Chitty Chitty Death Bang", there were flashbacks of Stewie in Lois' womb and the moment he was born, and his head was already like that. His half-brother Bertram has a similar head shape. It is possible that they may have inherited the shape of their heads from Nate Griffin's son. Another explanation could be that the head shape was inherited from Leonardo da Vinci, Stewie's ancestor, who in "The Big Bang Theory" had the same head shape.
Stewie has also demonstrated an ability to rotate his head into impossible positions, as seen in "North by North Quahog" and "Stewie Kills Lois". He has apparently developed a method of curing this as he keeps the phone number of an acupuncturist ready in his pocket, in "Stewie Kills Lois" Stewie asks Brian "Oh God, I've really screwed myself up here. Listen could you reach into my pocket and get the number for that acupuncturist?" O.J. Simpson and "Chris" threw Stewie's head like a football in "The Juice Is Loose". In "Extra Large Medium" Stewie has to dig a hole to put part of his head in, so that he could sleep on his side.
In "Yug Ylimaf", his grandmother Barbara Pewterschmidt comments on the unusual shape of Stewie's head shortly after he is brought home from the hospital, claiming it completes Lois' "little carnival."
Peter realizes he has taken the wrong baby in "The Most Interesting Man in the World" when the head shape doesn't match. He tries momentarily to squeeze the other baby's head to Stewie shape but Lois arrives.
- Death Has a Shadow - Mind Control Device - Used on a judge to save Peter from jail.
- Death Has a Shadow - Laser Gun disguised as a sandwich - used as another attempt to kill Lois.
- I Never Met the Dead Man - Weather Device - Used to control the world's weather and destroy broccoli.
- Chitty Chitty Death Bang - Carbonite Freeze Gun - Used on security guard that froze him for approximately 10 years.
- Mind Over Murder - Time Machine - Stewie moved time forward to bypass the pain of teething, but was forced to move time backwards when the machine's schematics became public.
- The Story on Page One - Hypnotic Control Device - A device used to harness the size and strength of Chris.
- Brian Does Hollywood - Mass Hypnosis Device - Used to control the unsuspecting public.
- Emission Impossible - In order to keep Lois and Peter from having another baby he created two machines:
- Peter-Bot - a robotic version of Peter that would replace him in the bed.
- Micro-Ship - A battle cruiser that shrank to the size of a cell, and was armed with phaser cannons to battle Peter's sperm cells; the ship's computer was voiced by Majel Barrett, widow of "Star Trek" creator Gene Roddenberry and voice of the ship's computer in all the Star Trek series.
- Peter Griffin: Husband, Father...Brother? - Tried to control the minds of a basketball crowd by taking the part of a head cheerleader.
- The Courtship of Stewie's Father - The little super villain makes a hovering drill machine to kill Lois, but it fails.
- Patriot Games - Stewie Invents his own version of the M2 Flamethrower, it is smaller, and it is blue, and works to a deadly and very painful level.
- Sibling Rivalry - Stewie gets into a war with his sibling, Bertram which involves his personal fleet of Stealth Bomber Jets.
- Stewie Griffin: The Untold Story - Created robot lookalikes of himself and Brian so they could leave and find his real father - Stewie's was believable but Brian's reflected what Stewie thought of him. They reappear in "Road to Rupert" and "Road to the North Pole".
- Road to Rupert - Creates a pair of skis with rockets on them that can even produce a large tea room and butler, so he can get his teddy bear Rupert back.
- Stewie Kills Lois - Stewie uses a simulation machine to see what it would be like if he killed Lois and took over the world.
- Lois Kills Stewie - The family finds a body switching orb that works on Lois and Peter.
- Road to Germany - Stewie created another time machine which Mort was mislead and thought it was a restroom.
- Not All Dogs Go To Heaven - Using blue prints he received at a Star Trek convention, he made a transporter to beam the cast of Star Trek: The Next Generation into his room, to ask them a few questions.
- Road to the Multiverse - He built a multiverse traveler.
- Quagmire's Baby - Clone machine to create deformed clones of himself and Brian named Bitch-Stewie and Bitch-Brian.
- The Big Bang Theory - Inadvertently causes the creation of the Universe.
- American Dad vs. Family Guy Kung-Fu II - He builds a robot walker complete with machine guns, lasers, rockets, a force field, and a metallic orb that can explode and kill his opponents.
- His lair is a large room hidden behind his bedroom wall and opened up when a baseball bat in his toy bin is moved.
- Roads to Vegas - Stewie builds a teleportation device that allows him and Brian to travel to Las Vegas, but instead creates duplicates of them at the destination.
In a possible future, seen in "Stu & Stewie's Excellent Adventure" he has a 9 to 5 job at Quahog Circuit Shack at 35 years old. He never had sex, killed Lois or took over the world. However, this may have been averted by younger Stewie's intervention.
- In the "Pilot Pitch", his now-yellow shirt was purple and his now-red overalls were green.
- In "New Kidney in Town" and "Business Guy" he says he wants to be a race-car driver.
- In "And I'm Joyce Kinney" it's hinted that Peter may not be Stewie's biological father, as there's a scene in Lois' porno movie Quest for Fur in which Lois was about to have sex with a man that looked a lot like Stewie.
- Due to the events of "The Big Bang Theory", Stewie is hypothetically 492 years old due to the fact he was in cryogenic stasis.
- In "Yug Ylimaf" it is revealed that Stewie was born at 11:34 a.m.
- Stewie has appeared as a Spokesperson for Snapvine.com, speaking as Darth Vader and asking users what they would blow up with the Death Star, while promoting the Lucas-MacFarlane project Blue Harvest.
- Stewie appeared in a short clip on the 20th annual MTV Video Music Awards insulting rapper 50 Cent.
- During the 2006 Canadian Election Royal Canadian Air Farce ran their own election with real candidates Paul Martin, Stephen Harper and Jack Layton, Jim Harris and "Stewie from Family Guy." Stewie ended up winning with 39 percent of the votes.
- Stewie has appeared on the MSNBC news program Countdown with Keith Olbermann, often introducing news stories regarding Bill O'Reilly.
- Stewie has also appeared in the DVD exclusive short of My Name Is Earl called "Bad Karma", in which he influences Earl to get even with everyone who's wronged him. Earl watches him on TV instead of Carson Daly. This short appears on the Season 1 DVD.
- Stewie was an announcer of the 2006 Spike Video Game Awards. 
- Stewie and Brian appeared at the 59th Primetime Emmy Awards performing "You Can Find It on TV" poking fun at networks and current shows on the air, while also poking fun at the new shows premiering that fall. The song was based on "The FCC Song" from "PTV".
- Stewie in parade balloon form appeared in a commercial for Coca-Cola that aired during Super Bowl XLII.
- In May 2009, Stewie appeared as a repeated hallucination seen by Agent Seeley Booth in the Bones episode, "The Critic in in the Cabernet."
- On Late Night With David Letterman on Monday, December 21, 2009, Stewie Griffin presented "The Top Ten Things You Don't Want to Hear From Your Child".
- At the 2010 Emmys on August 29th, Stewie appeared in a live-action skit with the cast of Modern Family.
- Stewie appeared in the April 20, 2008  episode of the comic strip Pearls Before Swine.
- In a Target Department Stores-sponsored advertisement for The Peanuts Movie, Stewie appeared dressed as Charlie Brown with Brian as Snoopy.