David Letterman: Sorry, Bruce Willis, you've been bumped by Obama

The previously scheduled guests on the Sept. 21 episode of "Late Show with David Letterman" were Bruce Willis and LL Cool J. Unfortunately for those two gentlemen, they'll have to wait. Instead, President Obama will be Dave's sole guest on the 21st.

The prez will be promoting his health care agenda on five, count 'em, five Sunday morning talking-head shows the day before his sit-down with Dave, but presumably he hopes to reach quite a different, less policy-wonkish audience on "Late Show."

The President appeared on "The Tonight Show with Jay Leno" back in March. He's no stranger to "Late Show," however -- this'll be his sixth appearance, albeit his first as president. He last appeared on the program back on Sept. 10, 2008.

For those curious about the competition, Conan's scheduled guests for that night are Ricky Gervais and Lynyrd Skynyrd.