08/26/2011 10:10 am ET | Updated Oct 26, 2011

David Letterman Wishes Regis Philbin A Happy Birthday (VIDEO)

It was Regis Philbin's birthday yesterday, and David Letterman celebrated the happy occasion by doing an entirely Regis-themed Top 10 List for him. Dave and Reege are, of course, longtime friends (one might even call them soulmates) and Regis has been a frequent guest on the "Late Show" for decades.

The list included lots of old-age jokes, but ended on a rather pointedly topical note. Can you guess what #1 was?