It all started much like it ended for David Letterman.
There he came, taking the stage at the Ed Sullivan Theater on Monday night, to a standing ovation and a chorus of chants of “Da-vid! David!”
The only difference this time was that Letterman, with a thick gray beard, was a guest on “The Late Show,” and Stephen Colbert, its host since 2015, led him to a chair that wasn’t behind a desk.
“Stephen,” Mr. Letterman said as he sat down. “Control your people!”
Letterman’s appearance on “The Late Show,” the series he started for CBS in 1993 and hosted until Colbert replaced him, somewhat solved one of the strangest mysteries in show business: Why didn’t he visit his successor? ?
Letterman has been no stranger to the spotlight since quitting his night job. He hosts his own long-running talk show on Netflix, “My Next Guest Needs No Introduction,” and has visited many other shows. He has done Jimmy Kimmel. abc program several times; Seth Meyers night show; Ellen DeGeneres Day talk show; Howard Stern radio show; Dax Shepard podcast; Marc Maron podcast; Conan O’Brien podcast. He even did Busy Philipps. podcast.
All of those appearances made his absence from Mr. Colbert’s show even more noticeable. After all, it is something of a television tradition that the great eminences of the night visit their successors.
jay leno has joined Jimmy Fallon on “The Tonight Show.” Jon Stewart visited his successor, Trevor Noah, on “The Daily Show.” Letterman, then at his rival CBS, visited Mr. O’Brien on “Late Night,” the 12:30 a.m. NBC show he had created more than a decade earlier.
Was being back at the Ed Sullivan Theater too much for Mr. Letterman?
Was it the fact that it took Colbert less than two years to become the late-night show’s most-watched host, a designation that eluded Letterman for most of his career?
Or was there something else at play?
In a 2015 interview with The New York Times, Letterman said he was initially bothered that he was not consulted about who would replace him. He also seemed surprised that Colbert had been cast so quickly after Letterman announced that he was retiring.
“You didn’t have to think about it much, did you?” he said in 2015. “I think it was the next day.” (Mr. Colbert was hired a week later.)
During their appearance on Monday, which took up more than 20 minutes of air time, Letterman and Colbert avoided the topic. Instead, Letterman talked about, among other things, visits to CVS pharmacies, his son leaving for college and how he arrived at the studio on Monday.
“I came to the show this afternoon and people were saying, ‘Yeah, can I help you?’” Letterman said. “And I said, ‘I’m Ed Sullivan.’ “I got fully involved.”
Colbert asked Letterman if he missed anything about hosting a late-night show.
“I miss everything,” Letterman responded. “Above all it’s fun. Very few things in life give you the opportunity (and I can’t speak for you on this topic), but for me, if you fail one, 24 hours later, you can try again.”
The ice may have been broken a few weeks ago when Letterman was a guest on “Strike Force Five,” a podcast that several of the current late-night hosts, including Colbert, started during the Hollywood writers’ strike. During the interview, Mr. Colbert took the opportunity to clarify how he had been hired.
For several minutes, Colbert explained that CBS executives first approached him in 2013 to discuss the possibility of replacing Letterman. At the time, Colbert said, he wanted assurances from CBS that Letterman was aware of this meeting. He was told that the network had Mr. Letterman’s blessing to meet with people.
Six months later, in April 2014, Letterman announced he was leaving “The Late Show.” But, Colbert explained on the podcast, he then received a strange message that made him wonder if Letterman really knew about the extension.
Letterman said on the podcast that CBS executives might have thought he was considering retirement, but that he had never explicitly told them to start searching for his replacement.
“I’m sure that part didn’t happen,” he said.
Letterman then recalled on the podcast how he had found himself in a similar situation years earlier, when NBC executives wanted him to host “The Tonight Show” part-time with Johnny Carson. When Letterman discovered that Carson was unaware of the deal, he refused to participate.
As Mr. Letterman’s appearance on the “Late Show” came to an end, he made a request of Mr. Colbert: Could I have a seat behind his desk? Mr. Colbert immediately stood up and gave his chair to Mr. Letterman.
While Mr. Letterman was behind the desk, Mr. Colbert had a question.
“Very few people know what it’s like to host one of these things,” he said, pointing to the back of his desk. “What do you think of my supplies? Was it anything like what you had down there?
“That?” Mr. Letterman responded. “All this grass?”
