The spirit of giving is alive and well across the country, especially at discount stores, where anonymous donors are paying off the layaway accounts of struggling strangers to make sure their kids get all the gifts on their Christmas lists. Here's what you should know:

What exactly to these good Samaritans do?
Typically, they call up Kmarts or Walmarts and ask to pay for Christmas gifts that impoverished parents have put on layaway for their kids. Many of the donors pay off all but a few dollars of the balance. That way, the layaway items remain in the store's system, and customers get a happy surprise the next time they show up to pay off part of their bill. "It made me believe in Christmas again," says Dona Bremser, an Omaha nurse, who got a call from Kmart telling her someone had anonymously covered the $70 remaining on $200 worth of toys for her 4-year-old son.

How did this trend get started?
It apparently began in Michigan, where a woman in her thirties showed up at a Grand Rapids Kmart earlier this month, walked up to the layaway counter, and asked if she could pay off somebody's balance. A confused clerk let her look for accounts in which toys had been set aside. The woman selected three. She paid about $500 — leaving balances of $10 in each account — and left a note on the receipts reading, "Happy Holidays from a friend." Then she disappeared.

Where else has this happened?
Since the story of that first mysterious donor was publicized, the same Michigan Kmart has received about $150 in donations per day. And copycat Secret Santas have popped up from California to South Carolina, where eight donors have contributed in a single store near Charleston. One man dropped off $2,000 to settle layaway accounts. In Indianapolis, a young father wearing "dirty clothes and worn out boots" arrived at a Kmart layaway counter with three small children, and said he wanted to pay something toward his bill but wouldn't be able to pay it all before Christmas. A woman then walked up and said, "No, I'm paying for it." When the father realized it wasn't a joke, assistant manager Edna Deppe tells the AP, "he just busted out in tears."

What is motivating these Secret Santas?
Many are simply inspired by the spirit of the season. In the Indianapolis case, the woman said that her husband had recently died, and she simply had more money than she could spend on just herself. After her stop at the layaway counter, she handed several people $50 bills, and paid for a cartful of toys a woman had at a checkout counter. In return, she asked people to "remember Ben," presumably her husband. "It was like an angel fell out of the sky and appeared in our store," Deppe said.

Sources: Associated Press, NPR, TIME