Jimmy Kimmel turned 50 recently, the age when men and women are encouraged to get their first colonoscopy. Instead of having the exam done privately, he chose to do it on camera in the hopes of encouraging more people to get screened.
Katie Couric asked to join Kimmel to the hospital because she's passionate about this cause. In fact, after her husband died of colon cancer at age 42, Couric went on national television herself and had a colonoscopy. After it aired, there was a 20% increase in the screenings. That jump has been called the "Couric effect." Now they're hoping for a similar outcome, ie. the "Kimmel effect."
Yes, you do get to see up Kimmel's ass but it's not (too) gross. It's for a good cause, and worth a watch.