In many countries and cultures, it's a tradition for cooks to hide a tiny charm in holiday foods to bring a bit of luck to the person who finds it.
According to ipsedixit, "during Chinese New Year we will often make dumplings (hundreds at a time), and my mom would generally stick a penny in one or make one loaded with sugar. The person who ends up eating the dumpling with the hidden penny or sugar is supposed to have extra luck in the new year." ipsedixit reports that similarly, the French hide a bean in La Galette des Rois (a.k.a. king cake), which is eaten during Christmastime, "so that the person who eats the pastry with the bean is crowned King for the day." (King cake is also served during Carnival in New Orleans.)
Quine says that coins are placed into Christmas plum puddings, and whoever finds one gets good luck. "And supposedly, everyone takes a turn stirring the pudding when mixing for 'luck' as well," Quine says. smartie has firsthand knowledge of this tradition: "My mum used to put money in the [Christmas pudding]—in ye olden days it was threepenny bits and one sixpence which was the 'prize' to get."
In Finland, "a screamingly delicious rice porridge" is served on Christmas Eve morning, woodleyparkhound says, and one blanched almond is hidden in the porridge. The nut will "bring good luck for the person who finds it in his or her portion," woodleyparkhound says.
And every year, EM23's Irish mother makes Christmas cakes (a whiskey fruitcake) and embeds surprises in them—"a ring for love and marriage, a coin for luck and wealth and a holy medal for good measure," EM23 says.
It's an American tradition, too. Sherri makes Hoppin' John—that Southern rice-and-beans dish—on New Year's Day, and it has become "a minefield of hidden objects" that signify good luck. The diners at Sherri's table could find a "penny for wealth, a small automobile signifying local travel with an airplane for longer trips," while "a starfish means someone is going to the beach this year, a (tiny) horseshoe for good luck, a (small) clown for merriment and a golden wedding ring for continued happiness," Sherri says. "We truly ought to have a dentist nearby when we dig in!"
But not everybody is happy to find the lucky charm. "I recall a family we used to celebrate Passover [with] would put a raisin or something edible and small into a matzo ball and if you got it, you had to tell a joke or a story or sing a song," MRS says. "I used to try to hide it in my napkin!!"