A mystery woman has popped up to help families pay their bills brandishing an American Express card at a Californian Toys R Us.

The woman, believed to be a retired grandma, delighted shoppers at the store in Culver City when she offered to pay for gifts for around 50 people.

The mystery shopper was joined by a “sidekick” who helped her pass an Amex card between the lines, according to a report by the Daily News.

“She was very quiet and unassuming and nobody in line had a clue what was going on,” shopper Laura Yoo told the daily News.

“People were excited and crying.”

Laura Yoo said the mystery woman paid for shopping for at least 50 people, many of whom had carts heaped with toys.

The woman’s assistant offered to pay for Laura Yoo’s own $54 bill after she bought gifts for her children.

“My boss would like to pay for your purchases today,” Laura Yoo recounted the sidekick as saying.

“I said, <<Thank you very much>> and gave a hug and she said <<Merry Christmas>>,” Laura Yoo told the Daily News.

Witnesses described the woman as at least 50, wearing a skirt, leather boots and a beret.

The woman would not give her name and has not been identified.

There has been a plethora of “layaway angels” in stores this holiday season, paying bills and debts in Kmart, Wal-Mart and Toys R Us stores across the country.

“It’s the Santa effect, really,” author and psychologist Elizabeth Lombardo told msnbc.com.

“It’s exciting and motivating and when people hear about it, they want to be in on it, too.”

More than $400,000 in layaway bills has been paid off at Kmart stores alone, according msnbc.com.

In one of the most recent examples of generosity, David Wilson, a car dealer from Laguna Beach, contacted a K-Mart in Costa Mesa, California after seeing a television report about donors paying off strangers’ outstanding accounts.

He asked the manager to tally up the balances on all the accounts with balances of $100 or less, and then wrote a check for $15,919.61 to pay off the total.