Torie Keene, from Florida, told the cashier at a McDonald's drive-thru that in the spirit of Christmas she wanted to pay for the meal purchased by the car behind her.
The cashier, Marisabel Figueroa, told Fox 13 that Keene had asked her to pass on a message to the woman in the car behind her.
Keene asked Figueroa to tell the driver to have a "Merry Christmas".
When Figueroa told the next car their meal had already been paid for by Keene, the customer was so touched that she decided to pay for the meal of the person behind her.
And so it continued.
"It kept going and going," Figueroa told ABC News. "After the 15th car I started tally marking the number of people that were participating on a piece of paper."
Figueroa, who worked from 9am to 3pm that day, said she kept giving each car the same message - that their meal had been paid for.
The pay it forward chain lasted almost her entire shift.
She added: "The customers were all so stunned and so happy. One lady even paid for the meals of the next three cars behind her.
"I feel very blessed to have been a part of all that."
Figueroa said after the story of the pay it forward chain reached the news, Keene - the woman who started it - reached out to say how pleased she was.
She said, according to ABC News that she was "only trying to brighten someone’s day".
Well, she definitely brightened more than one person's day.