I don't like to use language, but this...stinks!Edit
The death napkin is Frankie and Mike 's will, which is written on a ChiChi's napkin. In The SInkhole, it is found when Axl and Brick go through Mike's wallet. It is accidenally gets dropped in a bowl of milk and ruined. Frakie replaces it with a paper towel when Sue and asks the kids what they want. They look around realizing there is nothing they want.