I don't know why but when they are all in the panic room and then I believe they shove meg through a vent and they says "I hate you guys" (something to that degree) and stewie whispers "We hate you too *****. Aww could you imagine?"
I have no idea why I love it but I spit out liquid when I first saw it.
That and when stewie puts his babysitters B/f in a trunk and when he realizes it "Oh man Jeremy is still in the trunk... How long has it been, two weeks, yup two weeks.... he's dead."