After 33 years David Letterman signs off - in pictures

Stephen Colbert, left, host of the Colbert Report on the Comedy Central Network, has a laugh on stage with host David Letterman on the set of the Late Show with David Letterman, in New York. Colbert says on a visit to the late-night show he’ll take over next year he’s obviously “thrilled” to be succeeding David Letterman. AP

David Letterman riding a go kart powered by the reaction from mixing 648 Mentos candies into 108 two-litre bottles of Coke while taping a segment for The Late Show with David Letterman in New York. AP

Oprah Winfrey appears with David Letterman during a taping of The Late Show with David Letterman, in New York. Following the interview, Dave escorted Oprah across 53rd street to the opening of her new Broadway Show The Color Purple. AP

US President Barack Obama shakes hands with talk show host David Letterman on the Late Show with David Letterman in New York in this file photo taken September 18, 2012. Reuters

Actor Joaquin Phoenix, waves to the audience during his interview with David Letterman. Getty Images

This April 14, 2008 file photo shows David Letterman throwing a pitch to New York Mets third baseman David Wright outside the Late Show with David Letterman studios in New York. AP

In this Wednesday, September 25, 2013 photo provided by CBS, actor Robin Williams, left, joins host David Letterman on the set. AP

In this May 4, 2015 file photo, host David Letterman smiles during a break at a taping of The Late Show with David Letterman, at the Ed Sullivan Theater in New York. AP

A taxi drives by the Ed Sullivan Theater. EPA

David Letterman will host his final Late Show on May 20. Letterman said earlier this year he was retiring after more than 30 years as a late-night host, and CBS later named Stephen Colbert of Comedy Central as his replacement. We take a look back through time at some of his most memorable moments on the show.