Yiddish: What thief do you not apprehend? The one who steals the afikoman.

SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh.  The afikoman is half of a matzo which has been broken in two early in the Passover Seder, wrapped in a napkin, and set aside to be eaten after the meal. It is customarily stolen from its place on the table and hidden, and must be found in order to complete the Seder. This little diversion helps keep children awake and alert during the long evening.  NOTE: The literal translation of the verb tshepen is "to finger, to bother, to buttonhole."

וועלכן גנבֿ טשעפּעט מען ניט?  דעם וואָס גנבֿעט דעם אַפֿיקומן.

Velkhn ganef tshepet men nit?  Dem vos ganvet dem afikoymen.

What thief do you not apprehend?  The one who steals the afikoman.