David Letterman returns to "The Late Show" for first time since 2015 in "Colbert" appearance

Monday night's episode of "The Late Show with Stephen Colbert" featured a guest who needed no introduction: former host David Letterman. 

Letterman hosted the show for over 20 years, from 1993 to 2015. His appearance was his first time he had returned to the Ed Sullivan Theater, where the show is filmed, since his retirement eight years ago. 

The audience greeted Letterman with a warm welcome and booming applause as he sat down as a guest with Colbert. Even after he took a seat, the crowd continued to chant his name.