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Letterman, Stewart sing happy birthday to USO with Obamas

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David Letterman's job at the USO event, where he appeared with President Obama and first lady Michelle Obama, was to introduce the cake, which he described as "beautiful, and I'm told mostly inedible." (AP Photo/Cliff Owen)

Comedians David Letterman and Jon Stewart helped President Obama and first lady Michelle Obama wish the United Service Organizations a happy 75th birthday.

The Obamas, Letterman, Stewart and Vice President Joe Biden were on hand at Joint Base Andrews in Prince George's County, Md., to kick off the celebration for the military family organization's big anniversary.

Stewart was tapped to introduce Biden, and said, "He is always a guy we have fun with because he is always unpredictable."

The former "Daily Show" host also told all the USO members in attendance that "we need to get the whole country involved and tell your story."

Letterman's job was to introduce the cake, which he described as "beautiful, and I'm told mostly inedible."

Before doing that, he recounted a story about how someone earlier in the day had mistaken him for poet Walt Whitman because of his bushy retirement beard. While the crowd was laughing, Obama quipped, "I can see that, Dave."

He also used the opportunity to thank the USO for taking him to perform in Afghanistan in 2002, and Iraq in 2003 and 2004.

"It was, as anyone can tell you, a life-changing experience. And I would like to thank them for that opportunity," he said.

The former "Late Show" host ended on a very culturally relevant joke about the rest of the evening's festivities.

"You are in store tonight for what will be … the best show in the United States tonight," he said. "Except maybe 'Hamilton.'"