What to do?

Oh, yes, the Late Show with David Letterman.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, made his inaugural appearance on the show Monday.

Mullen played it straight, even through some good-natured ribbing about his career and about the national security establishment.

When Letterman tried to draw Mullen out on the killing of Osama bin Laden — and exactly what the chairman and other officials were looking at in the Situation Room that day — the chairman demurred.

At one point, Letterman, looking at the now-famous photo of the scene, pointed to Antony Blinken, national security adviser to Vice President Biden.

“This guy’s not supposed to be there, right?” Letterman cracked. “He’s not supposed to be in there. He just wandered in off the tour.”

Mullen did address the extraordinary preparation that took place ahead of the mission and the performance of the two pilots whose helicopter went down in Abbotabad.

“Each of them performed at an exceptionally high level, and both of them — all of the pilots — made extraordinary contributions to the success of this mission,” he said.

So, who’s funnier, Mullen, who can be famously tongue-tied, or Defense Secretary Robert M. Gates, who is well-known for his corny jokes?

Neither. Betty White, who read the Top 10 list before Mullen’s appearance Monday night, gets the prize.

(No. 6 tip for living a long and happy life: Avoid Tweeting any photos of your private parts.)