David Letterman celebrates 20 years of the "Late Show"

(CBS News) Bill Murray stopped by the "Late Show with David Letterman" Thursday night to help Letterman celebrate an historic 20-year run behind the desk of the CBS late-night comedy show. The show shared a look back on two decades of self-deprecating, zany comedy:

Murray was Letterman's first guest at The Ed Sullivan Theater in New York City on Aug. 30, 1993. Then-president of CBS, Sir Howard Stringer, said that in the beginning of the show's run, "The Late Show" team felt like "the orphans of late night," up against the gold standard of NBC's "Tonight Show."

Despite being widely considered to be Johnny Carson's heir apparent, NBC tapped Jay Leno for the role, and Letterman -- his pride wounded -- signed a $14 million contract with CBS.

"We ended a period of weakness and turned it into a period of strength and no one has ever really argued by it, because he stands for something and it fits. It fits the definition of CBS," Stringer said.

Twenty years later, the "Late Show" has won nine Emmys and been nominated for 64 more. Last year, Letterman was celebrated for his award-winning comedy at the Kennedy Center Honors.

Along the way, band leader Paul Shaffer has been by Letterman's side. At the start - when they occupied the 12:30 slot on NBC - Shaffer said, "We were making fun of talk shows, ourselves included, we're still certainly doing that, but we are now the, we are the talk show I think. Dave is the first to make fun of himself."

And while Letterman himself has said he does not see much past a 25th anniversary of the show, Shaffer warned CBS News' Anthony Mason from making any predictions on that front.

"No one knows. We've never known our future in this nutty business we call show, anything can happen," Shaffer said, adding, "Meanwhile, anything can happen."

Now in its 21st season, the "Late Show with David Letterman" airs weeknights at 11:35 p.m. ET on CBS.