WASHINGTON (AP) — President Joe Biden and first lady Jill Biden brought some Christmas Eve cheer to hospitalized children who aren’t well enough to go home for the holidays.

It’s a longstanding tradition for first ladies to visit Children’s National Hospital at Christmastime, but Joe Biden’s visit on Friday was a surprise. It marked the first time that a sitting president had joined the fun, the White House said.

It wasn’t the only tradition that the president joined in on Friday. Jill Biden answered calls to the North American Aerospace Defense Command’s Santa tracking service, another longstanding tradition for first ladies, and she was joined by Biden for the calls.

At the hospital, the Bidens spoke with a group of children making lanterns as part of a winter craft project, asking each one what they drew on their lanterns. Some drew family, snowmen or other holiday-themed art.

They both spoke to a child who said the hospital “helped him when he was down.”

“Well we hope we’re bringing you some joy today,” Jill Biden responded.

The president added, “You’re bringing us some joy, pal.”

Biden also pulled out his phone to show the kids photos of his new dog, Commander, a nearly four-month-old German Shepherd puppy. The dog joined the family this week and was seen playing with a handler on the South Lawn of the White House complex earlier Friday before the Bidens left for their visit to the hospital.

“His name is Commander!” Jill Biden told the kids. “And this morning he was eating my slippers!”

The president and first lady then sat before the hospital’s Christmas tree, where Jill Biden read “Olaf’s Night Before Christmas” to the kids, which was broadcast to hundreds of children in their rooms at the hospital.

The Walt Disney Co. provided copies of the book for each patient so they can follow along with the first lady, the White House said. Each book includes a White House bookmark designed by her office.

The annual tradition of a hospital visit by the first lady dates to Bess Truman, who served in the role from 1945-1953.

Before returning to the White House, the two stopped briefly at a Jill Biden-themed Christmas tree set up on the street in D.C.’s Dupont Circle neighborhood by a local business owner. The president hung the 2021 White House Christmas ornament on one of the branches, nestled between large cutouts of Jill’s face dotting the tree.

Back at the White House, the two capped off their Christmas Eve festivities by answering calls for NORAD, as they watched Santa soar over the United Arab Emirates on the Santa tracker screens. They took three largely pleasant phone calls from kids and parents, though one father capped off an otherwise polite conversation with the president by wishing him a happy holidays and adding, “Let’s go Brandon!” before hanging up. The phrase has become widely used by conservatives as a stand-in for a more vulgar epithet against the president.

Biden didn’t seem to catch the caller’s intent, however — he responded, “Let’s go Brandon, I agree” as the call came to an end. The White House did not respond to a request for comment on Biden’s response.

AP writer Darlene Superville contributed reporting.