In order to unlock Ducken, your monster must be fed cup jellies. At random intervals, after the monster has eaten, a diamond mark may be found on the lid. After five marks have been collected, Coltia will mail the marks off to obtain a Quack Doll. When combined with the Strong Glue, it creates a secret seasoning for creating a Ducken.
In Monster Rancher DSEdit
Cup Jellies cost 250g per month and slightly decrease your monster's Fatigue.