Elliott Shirback was in a grocery store with his mother, Anne Daggett, in Niagara Falls, N.Y., when he heard something hurtful from another customer.

"You left your idiot kid in the lane," a man told Daggett. He was referring to Shirback, 25, who has Down syndrome.

Daggett said she asked her son what would cheer him up and he responded, "100 Christmas cards."

So Daggett took his request to her Facebook page.

"If anyone could send him a card, he would love it," she posted on Dec. 18.

Within days, thousand of cards had arrived at their home. They came from Germany and Great Britain. In the latest batch that came in the mail today, there was a Christmas card from Paris. Another woman sent four four-leaf clovers for good luck.

"It makes me really feel like the cool dude I am," Shirback told ABC News.

Shirback and others wanted to take a moment with ABC News to cheer the everyday people who took a second out of their day this busy holiday season for random acts of kindness.

For Dana Hoffman and her daughter Emily in LaGrange, Ohio, it was finding a bag of presents that had fallen from the roof of a car.

"I was just hoping that somebody out there would know somebody that lost these gifts," said Hoffman, whose husband found the bag in the middle of the road on his way home.

The gifts were clearly for a little boy and included Christmas cards to a child named Zach.

Using social media, they were able to reunite the package with its family.

Others played Secret Santa by leaving $1,000 tips for waiters signed "Tips for Jesus." Good Samaritans also paid layaway bills - often buying armfuls of toys for families - at Walmart stores across the US.

Watch: Waitress reacts to receiving a $500 tip at Friendly's.

Karen Fowler of Hendersonville, N.C., said the charitable acts had put her faith back in mankind.

She and her family had put a toy monster truck on layaway for her 5-year-old grandson. The family said that times had been hard and that the free gift had meant a great deal.

"It's not much to a lot of people but to me it's a million dollars," she said. "It made a little boy very happy. It really did."

At Elliot Shirback's home in upstate New York, the cards were still coming in.

Daggett read one from the Phillips family in Endicott City, Md.

"Remember - even when people are mean, there are even more people who are nice and spread their love. Happy New Year!"