I'm so sorry, I was on the road, haven't click the replies section! :(
But I read Idiot on my language about a month ago, I never read Dostoevsky in English, because my language is similar to Russian, so it's kind of fun to this :)

The whole second chapter with Mishkin is so witty so I can't choose one quote, but a small scene from the first chapter would be:

The old fellow went straight off to Nastasia Philipovna, touched the floor with his forehead, and began blubbering and beseeching her on his
knees to give him back the diamonds. So after awhile she brought the box and flew out at him. ‘There,’ she says, ‘take your earrings, you wretched old miser; although they are ten times dearer than their value to me now that I know what it must have cost Parfen to get them! Give Parfen my compliments,’ she says, ‘and thank him very much!’.

Such strong scene, you almost feel the shame yourself, and you feel this is just a begging of what's to come.