Doctor: Mrs. Simpson, I'm sorry, but your husband suffers from a persecution complex, extreme paranoia, and... bladder hostility.
Marge: Doctor, if you just talk to him for five minutes without mentioning our son Bart, you'd see how sane he is.
Doctor: You mean there really is a Bart? Good lord!
Leon Kompowsky: [In Michael Jackson's voice] Hi, I'm Michael Jackson from the Jacksons.
Homer: I'm Homer Simpson, from the Simpsons.
Bart: [singing] Lisa, her teeth are big and green. Lisa, she smells like gasoline. Lisa, ta-ra-ra Lisa. She is my sista, her birthday I mista.
Leon Kompowsky: We call this one the Chief. He's been here since 1968. Never says a word. Never moves a muscle.
Homer Simpson: Hey.
[All the doctors gather around muttering and writing notes]
Chief: Well, it's about time someone reached out to me!
[Homer is calling home from a mental institution]
Bart: Joe's Taxidermy. You snuff 'em, we stuff 'em.
Homer: Boy, when I get home, I'm gonna wrap my hands around your neck and...
[noticing the orderlies glaring at him, he relents]
Homer: ...smother you with kisses.
Bart: Homer, whatever they've got you on, cut the dose.
[answering the phone]
Bart: Joe's Crematorium. You kill 'em, we grill 'em.
Homer Simpson: I can't wear pink! Everyone at work wears white! I'm not popular enough to be different.
Montgomery Burns: Why is that man wearing pink? Smithers, who is that?
Waylon Smithers: Homer Simpson, one of your boobs from sector 7-G.
Montgomery Burns: Simpson, eh? Judging from his attire, he must be some kind of free-thinking anarchist.
Waylon Smithers: I'll alert security.
Montgomery Burns: Excellent! These color monitors are already paying for themselves.
Homer: [Being shown an inkblot that looks like Bart] THE BOY!
Leon Kompowsky: You know Bart, when I was growing up I didn't have much money. So you know what I did every time my sisters' birthdays rolled around?
Bart: Stiffed them?
Leon Kompowsky: No Bart, I wrote them a song to show them I cared.
Bart: I can't write a song! I'm only ten.
Leon Kompowsky: ONLY ten?, When I was your age, I had six Gold records.
Bart: Hey, Looney Tunes!
[pulls out the Thriller album]
Bart: THIS is what Michael Jackson looks like! You just look like a big, fat mental patient!
Leon Kompowsky: You'd be amazed how often I hear that, Bart.
Homer Simpson: [Trying to scrub off stamp that reads "insane"] Come off! I'm sane now!
Doctor: After analyzing your husband, we have determined that he's not a danger to anyone.
Homer Simpson: That's the nicest thing anyone's ever said to me. Can I have it in writing?
Bart: [Lisa wakes up Bart] Lisa, it's 6 a.m., what's wrong? Dad died?
Lisa Simpson: No, no, no, he's fine.
Bart: Whaddya know, I'm relieved!
Bart: [Bart gets a phone call saying Homer has been committed to a mental institution] Mom... Dad's in the nuthouse!
Homer: Lisa, you like homework. Would you fill out this form for me?
Lisa Simpson: Well, all right - if you listen to the poem I just wrote.
Homer: D'oh...! Uh, okay.
Lisa Simpson: "Meditations on Turning Eight," by Lisa Simpson. "I had a cat named Snowball, she died, she died! Mom said she was sleeping, she lied, she lied! Why, oh why is my cat dead? Couldn't that Chrysler hit me instead? I had a hamster named Snuffy, he died!"
[that's all she wrote, literally]
Homer: No deal.