The opening sequence of “Elf the Musical” might make you think, “Oof.”

Will Blum as Buddy in Elf the Musical. (Courtesy Kennedy Center)

The musical, opening Tuesday at the Kennedy Center, is based on the 2003 Will Ferrell movie about a human who thinks he’s a Christmas elf — even though he towers over the rest of his Lilliputian friends.

“Everyone goes in expecting some sort of effect, whether it will be short actors or children” to play the elves, says choreographer Connor Gallagher.

(Kyle T. Webster for the Washington Post) (Kyle T. Webster for the Washington Post)

Instead, it’s full-grown adults playing the roles. But they are walking on their knees any time the musical shows a scene from the North Pole.

It looks like it hurts, but don’t worry: Their elf shoes are actually kneepads, and to preserve the illusion, they wear stockings that blend in with the stage floor.

“We wanted to take what is traditionally a tap number and put it on the elves,” Gallagher says. “I think it challenges all of the dancers’ skill sets.”

The elves also must be able to toss and catch packages across the workshop, which can be difficult because of the lack of mobility. Some of the elves even do flips. And while it can be tough on their knees, the scene is short enough that it doesn’t cause harm, says Gallagher. In rehearsal, they wear even thicker volleyball kneepads.

“They’re so used to it now,” Gallagher said. “You just have to condition your body to doing it.”

More from our Winter Whimsy issue:
Holiday plays, categorized
A holiday guide for Grinches
A childless adult's guide to ICE! at National Harbor
One perfect holiday date
5 classic holiday drinks
Christmas Day dinner and a movie