David Letterman, Paul Shaffer and the gang at the Ed Sullivan Theatre celebrated 19 years with CBS on Thursday night’s edition of Late Show with David Letterman.

Just as impressive — if not more so? Letterman invited stand-up comedian Brian Regan onto the anniversary program to perform for his 25th time with Dave.

Twenty-five!

For this set, Regan explores how a roofing company missed out on a genius naming opportunity, Boeing’s unusual advertising campaign, and corporate accountability — or lack thereof. Whatever happened to the customer is always right?

Roll the clip!