"A lot of people have been affected by Dave, but I don't think anyone in show business more than me," Romano told ET's Brooke Anderson. "I don't think a lot of the public knows that he was the reason that I had a sitcom. After 11 years of standup, I got my first Letterman spot. After that spot, he signed me to a deal to develop a show. That show was Everybody Loves Raymond."
Romano first appeared on Late Show in 1995. Now, 20 years later, Romano will assist in Letterman's grand sendoff. Fans will see it all in Monday's tribute, including Stupid Human Tricks and Letterman's best Top Ten lists.
"You're going to see people who were on in '82," Romano said. "You see them over the years getting older. And some of the stuff that Dave doesn't do anymore."
In his 33 years as a late-night host, Letterman has led more than 6,000 shows. The icon has been around long enough to have some of his first young viewers become his contemporaries.
"He recognizes because of his age and how he lines up with the other late-night hosts that he's competing with," The New York Times' Dave Itzkoff said. "Younger people like Jimmy Kimmel and Jimmy Fallon that the audience is starting to go elsewhere and they want to see hosts of a different stripe and he knows he can't keep up with it forever."
The guest list for Letterman's remaining episodes is extraordinary: Bill Murray, Will Ferrell, Tina Fey, Jack Hanna, Scarlett Johansson, Michael Keaton, Steve Martin, Don Rickles and Martin Short to name a few.
Like he has done for the past three decades, when the final episode comes around on May 20, Letterman will make it his own.
"I did ask him if he was going to take any cues from Johnny Carson, which was very memorable because it was just Johnny sitting on a stool essentially talking to his audience," Itzkoff said. "Letterman said that he doesn't want to copy that."
David Letterman: A Life on Television airs May 4 at 9:30 p.m. ET/PT on CBS.