My first encounter with David Letterman on television was on the original Peter Marshall-hosted THE HOLLYWOOD SQUARES where Dave answered a question with a surreal word image of his dog filling out tax returns.
Afterwards, I became a regular viewer of 1980's short-lived THE DAVID LETTERMAN SHOW on NBC (which, in the Wichita Falls TX market, was replaced for a time by reruns of MEDICAL CENTER). In that incarnation, Dave dared to ignore the rules for daytime TV talk shows and gave airtime to comic/musical talents such as Valri Bromfield, Loudon Wainwright III and Andy Kaufman (though, occasionally, Dave's infatuation with old-line showbiz would surface when Allen "PASSWORD" Ludden would come on and disdainfully mock pop song lyrics). And, if I recall correctly, Edwin Newman would occasionally deliver brief news bulletins.
LATE NIGHT WITH DAVID LETTERMAN debuted in early 1982--the purest form of Letterman's irony, sarcasm and demythologizing of television conventions.
A decade later, Dave was denied THE TONIGHT SHOW in favor of then-Monday night guest host Jay Leno.
1993 heralded the move to CBS with the re-titled LATE SHOW WITH DAVID LETTERMAN. On its debut show, Paul Newman stood up and asked "Where the hell are the singing cats?" This turned into a prophetic statement heralding the departure or minimization of old NBC colleagues such as Riquette, Kamar the Discount Magician and Larry "Bud" Melman (who, on CBS, had to go by his real name of Calvert DeForrest due to NBC spouting nonsense about "intellectual property")
No need to bemoan it here, but about 80% of the idiosyncrasy was drained from the CBS Letterman show because of the concerns over what made for an appropriate 11:35 p.m. show vs. an appropriate 12:35 a.m. hangout destination.
As Dave aged, his energy level began to decline. In recent years, outside incidents such as the WGA strike and Jay Leno/NBC's demoting Conan O'Brien from THE TONIGHT SHOW seemed to periodically reanimate the peak-era Letterman.
I haven't been a regular viewer of LATE SHOW WITH DAVID LETTERMAN in quite a long time, but am planning to watch the final two shows via DVR and herald the end of a talk show era quite different from the current "invite guests to play parlor games" ethos.