Gilmore Girls

[Michel is railing at Lorelai for mentioning his eating habits to his doting mother in passing.]

Lorelai: I just assumed, since you gave up carbs a year ago, she knew. 

Michel: [angrily] Yes! Well, you know what happens when you assume?

Lorelai: What?

Michel: I don't know! S-something about a donkey! It's a… stupid American phrase!