In one of the quirkiest episodes of Happy Days, "Chachi Sells His Soul," Chachi sells his soul to the devil's "nephew” to become a more "warm and wonderful" person.

Recognizing his cousin is cursed, Fonzie rushes to make his own deal. He agrees to go 24 hours without kissing any chicks, and if he can go just one day without being a ladykiller, then Chachi gets his soul back.

It's no secret that when Happy Days premiered, Fonzie became an overnight heartthrob, with girls all over America wishing they could be the girl on Henry Winkler's arm. Before the show even premiered, Winkler already felt as popular as the Beatles, being greeted by screaming fans.

But of all the fan encounters with the Fonz, there's one kiss in the mix that we think is perhaps the sweetest story in Winkler's career.

Five-year-old Julia Tomanelli lost the vision in her left eye during surgery to remove a tumor when she was only three years old. Over years spent receiving treatments and recovering at New York Hospital, while the vision started fading from her one good eye, she loved watching Happy Days.

So when her parents asked her what she wanted for Christmas in 1975, the little girl had the Fonz on her mind.

"I want to have Fonzie's picture and his autograph," she requested, pointing at the TV when she said it, as if Fonzie lived inside there.

Her parents thought this was doable, but then Julia added, "And I'd like him to talk to me in real life."

Julia was about to undergo what The Daily News called "the most critical two weeks of her life." That Christmas, she would find out if her most recent surgery was a success.

Julia needed a win. But even she didn't expect the Fonz to come through.

And then her phone rang.

"A-y-y-y, this is The Fonz," the voice on the line said.

"Fonzie?" Julia answered. "I think you might be joking, but my name is Julia."

"No joke, Sweetie Pie," Winkler responded. "I thought it would be nice for Christmas if we spoke to each other for a little while."

On the phone, they talked about the autographed black-and-white photo he sent, and Winkler promised to send her one in color, too. She told him how much she loved the show and nearby, her family beamed at her bedside, listening in.

The family reported Julia's face was lit up the entire time.

Before getting off the phone, Fonzie made a special request of his own.

"Would you do something for me, Sweetie Pie?" he asked.

"What?" Julia wondered.

"Would you give me a kiss?" The Fonz requested.

The five-year-old smacked her lips against the receiver, and to her delight, the Fonz smacked his lips back, mwah!

"God bless you, Sweetie Pie," Fonzie said.

"You, too," Julie answered.