David Letterman has told how he was mistaken for Dick Van Dyke.

The former talk show host, who helmed The Late Show with David Letterman for 22 seasons, admitted that people might have forgotten exactly what he looks like since he finished his show in 2015.

"Here's what happens to me now: People used to know who I am and now I have to wear a name tag to get anything going," he joked on Jimmy Kimmel Live.

He then recalled that he met someone at his local farmer's market who he thought was a fan.

"A guy comes up to me and he says, 'Excuse me, are you who I think you are?'" he said. "And now, I'm all loaded up and I respond, 'Well, that depends on who you think I are.' That always gets a big laugh."

He continued, "He said 'Dick Van Dyke,' and I said, 'No.'"

Letterman is 78, while Van Dyke turns 100 this weekend.

He also recalled how the age of his fans has changed significantly over the years, saying that many years ago, fans would come up to him and tell him they watched his show.

"Then, somewhere down the line, they started to say, 'Oh my mother watches you now every night and she really misses you now that you're gone.' Here, lately it's 'You know what, I'd like a picture of you to show to my grandfather - and his father also. We used to watch it together in the hospital...' Just like that," he said.

Letterman's Netflix talk show, My Next Guest Needs No Introduction, is about to air its new season.