A look back at some of David Letterman’s most memorable moments

David Letterman used to joke that “there is no off position on the genius switch.”

But on May 20, he’ll pull the plug on his talk show and take his final bow on the stage of New York’s Ed Sullivan Theater.

The “new king” of late night will retire after logging over 6,000 hours spread over two networks and 33 years.

He survived heart surgery, a sex scandal, and the second coming of Jay Leno. At 68, surrounded “by Jimmys” in what has become a crowded late night field, he followed his hero Johnny Carson’s cue and decided to walk away.

For many of us who grew up with him, there is an attachment to “Dave” that goes beyond longevity. As Jimmy Kimmel says, “He’s the talk show host of our lifetime.”

Letterman was always admired — and sometimes feared — for his sharp wit. On his original NBC series, he brought a jeans-and-sneakers, frat house casualness to late night, enticing college crowds by tossing melons off rooftops and leaping onto walls with Velcro suits.

In Paul Shaffer he had a bandleader who could score any situation and jam with a who’s who of rock ‘n’ roll. Together they rode a wave of irony in American comedy.

Letterman’s most astonishing legacy, however, may be how he evolved and grew as a broadcaster. In 33 years, he went from being a gap-toothed, counterculture smart-ass to a respected father figure more at home with presidents than pop stars.

The evolution came in stages. Here, as Letterman might say, are the Top 10 milestone moments from his career:

July 28, 1982: Comedian Andy Kaufman and wrestler Jerry Lawler appear to get into a fight on the show. Turns out it was all staged.

Nov. 13, 1987: Letterman badgers Sonny & Cher into singing — for the last time together — “I Got You Babe.”

May 22, 1992: Johnny Carson’s last “Tonight Show.” Jay Leno got the job Letterman thought was his. The war for late night was on and Letterman was motivated like never before.

Aug. 30, 1993: Letterman makes his CBS debut and Paul Newman, Bill Murray, Billy Joel — and the ghost of Ed Sullivan —help make it a memorable night. A staggering 23 million viewers tuned in.

May 13, 1994: Johnny Carson makes a rare post-“Tonight” appearance, walking out to Dave’s desk with the night’s Top 10 list. He sat down, took in the thunderous applause, turned and walked away.

April 12, 1995: Drew Barrymore gets up on Dave’s desk and flashes him for his birthday. Letterman could never hide his crushes on Barrymore, Teri Garr, Julia Roberts, Amy Sedaris, Isabella Rossellini and Mary Tyler Moore.

Feb. 21, 2000: Letterman returns a changed man after quintuple bypass surgery. Bill Cosby, Regis Philbin, Tom Green and others hosted in his absence.

Sept. 17, 2001: About a week after the 9/11 attacks, with New York still reeling, Letterman went back on the air and calmed viewers across North America. “There is only one requirement for any of us,” he said, “and that is to be courageous. Because courage, as you might know, defines all other human behaviour. And I believe, because I’ve done a little of this myself, pretending to be courageous is just as good as the real thing.”

He went on to praise firefighters and police officers, declare New York “the greatest city in the world,” and denounce the attackers. Gravitas in late night? A door had been opened to Jon Stewart, Stephen Colbert, Bill Maher and others.

Jan. 30, 2009: Having ended his feud with Oprah Winfrey a few years earlier, Letterman set out to right another wrong. He invited the mother of stand-up comedian Bill Hicks onto the show. Letterman — new to CBS and locked in a ratings war with rival Leno — had cut Hick’s edgy stand-up act from an October 1993 show. Unbeknownst to Letterman at the time, Hicks had pancreatic cancer and died the next year. Letterman admitted his mistake and showed the act 16 years later.

Oct. 1, 2009: A humbled Letterman admits affairs with staff members in order to quash an extortion attempt. Instead of derailing his career, his straight-up confession is seen as a textbook example of how to quickly deal with a crisis. He even got away with joking about it. “I got into the car this morning,” he said soon after, “and the navigation lady wasn’t speaking to me.”