The riddle
Who Is Never Hungry During Christmas?
Stuffed, twice over
To stuff, in Merriam-Webster, is to fill, and stuffed is the result. In the kitchen, a turkey is stuffed when its cavity is filled with a seasoned mixture of bread and other ingredients. In casual speech, a person who has eaten too much is stuffed too. The riddle puts the two meanings in one word: a turkey full of stuffing cannot be hungry.
Stuffing or dressing
The mixture goes by two names in the United States. Merriam-Webster lists dressing as another word for stuffing, and in many households only one of the names is used. The riddle uses the verb, which does not depend on which name a family prefers.
A third use of the word
The same word turns up in other phrases. A stuffed nose is a blocked one, and a stuffed shirt, in Merriam-Webster, is a pompous person. None of these meanings is in play here, but they show how many jobs the word has. The riddle picks the two that fit a dinner table. A group can hunt for other words that mean one thing in one sentence and something else in the next, and see which pairs make a riddle worth asking.
Why the setting matters
The question assumes that a meal is on the table and a turkey is the centerpiece. Pause after "hungry" before saying the answer. A listener who thinks of people usually guesses a cook or a guest, and the answer shifts the focus to the food itself.