Because he's awesome, that's why!
Lois Griffin: Come on Stewie, don't be afraid. It's just water, it's not gonna bite. Stewie Griffin: Shut up! I know it's not going to bite, stupid! What a stupid thing to say. You drown in it you moron! It doesn't have to bite you!
Meg Griffin: Can I be in the play, Mom?Stewie Griffin: Oh yes, you can be the dumpy teenage girl who cries backstage because no one finds her attractive.
[watching cheerleaders changing in a locker room] It appears my wee-wee's been stricken with rigor-mortis.
Meg Griffin: Everybody! Guess what I am?Stewie Griffin: Hm, the end result of a drunken back-seat grope-fest and a broken prophylactic?
Stewie Griffin: [hitting on some co-eds] I must say, the most recent campus sporting event was quite spectacular.Co-ed: Aw. Are you in a fraternity, little boy?Stewie Griffin: Not yet, but I'm thinking of joining I Felta Thigh.
Lois Griffin: I'm gonna go get some oranges Stewie. Here, hold the rest of these bags for mommy.Stewie Griffin: Oh, what brilliant parenting Lois. Leave a tiny infant with a plastic bag. You know I might asphyxiate myself just to teach you a lesson. Here I go. Just like that boy from INXS…[Stewie tries to put bag over top of his head.] I'm going to do it! [Tries to put bag over left side of his head then climbs into it and tries pulling it over his head.] BLAST! Good Lord Lois, either I was a c-section, or you're Wonder Woman!
Lois Griffin [finding note in Chris's pocket]: Huh, what's this? You know Stewie, Mommy doesn't usually read things out of Chris's pocket. She's more respectful than that.Stewie Griffin: Whatever helps you sleep at night, bitch.
Lois Griffin: Oh, I haven't been on a college campus in years. Everything seems so different.Stewie Griffin: Really? Perhaps if you laid on your back with your ankles behind your ears that would ring a few bells.
Stewie Griffin: Lois! Lois! Lois! Lois! Lois! Mom! Mom! Mom! Mommy! Mommy! Mommy! Momma! Momma! Momma! Ma! Ma! Ma! Ma! Mom! Mom! Mom! Mom! Mommy! Mommy! Momma! Momma! Momma!Lois Griffin: WHAT!?Stewie Griffin: Hi. [runs off giggling]
Oh I feel so delightfully white trash. Mommy, I want a mullet.
Lois Griffin: What's going on down here? Stewie Griffin: Oh, we're playing house. Lois Griffin: That boy's all tied up. Stewie Griffin: Roman Polanski's house.