WATCH: Barack Obama turns into Santa, brings smiles to children's faces in hospital

Barack Obama, donning a Santa Claus hat and a bulging sack slung over his shoulder, made a surprise visit to a children's hospital here and delivered gifts to young patients ahead of Christmas. The former US president visited the young patients at the Children's National Hospital in Washington on Wednesday.

First on his list was a group of patients 4 and up who were making snowflakes in one of the hospital's playrooms, The Washington Post reported. The 57-year-old handed out jigsaw puzzles Hot Wheels sets, remote-control cars, and glittery nail polish, among other goodies collected by Obama and his staffers. 

"I just want to say thank you to all of you guys," Obama told the hospital staff, who greeted him with rapturous cheers, in a video he shared on his Twitter account. "We've had the chance to talk to some of the wonderful kids and their families," he said in the video, which has gone viral with over 242,000 likes. "As the dad of two girls, I can only imagine in that situation to have nurses and staff and doctors and people who are caring for them, and looking after them... that's the most important thing there is," he said.

The 44th US president also dropped by individual patient rooms for one-on-one visits with children and their parents. He gifted one 12-year-old patient who was nervous about heading to high school next year a piece of advice: "Even the cool kids don't have it all figured out."

"I know they will be talking about it for years to come," said Kurt Newman, chief executive and president of Children's National Health System.  "At such a busy time of year, when no one wants to be in the hospital, his natural warmth lifted the spirits of those kids, their parents and of each staff member he met along the way," the Post quoted Newman as saying.

Before leaving, Obama thanked the staff for working during the holidays and recorded a video message to be played on the hospital's internal TV system for those he was not able to visit during the trip. 

Obama also retweeted the Hospital and sent them Christmas greetings.

Only a handful of the Children's National staff knew that the president was coming to town, but word spread quickly during the 90-minute visit. 

By the time he was headed for the door, a crowd had gathered at a nearby nursing station. The group of doctors, residents and nurses cheered for Obama before busting into an impromptu rendition of "We Wish You a Merry Christmas."

Obama, who demitted office in 2017 after serving two terms, lives in Washington