Letterman
David Letterman will end his 33-year run as a late-night TV host on Wednesday, May 20, 2015. Reuters

Television is going to look a bit different on Thursday. After more than 30 years of being a late-night fixture, David Letterman will sign off on Wednesday. No guests have been announced for the last episode of "Late Show With David Letterman," but knowing the history of the late-night show, anything is possible. Let's take a look back at some memorable moments.

Memorable Guests

Letterman didn't start out on CBS. "Late Night With David Letterman" ran after NBC's "The Tonight Show" with Johnny Carson from 1982 to 1993. The fallout from NBC's decision to go with Jay Leno as Carson's replacement and not Letterman is part of TV lore. "Late Show With David Letterman" premiered on CBS on Aug. 30, 1993. The first episode featured Bill Murray and musical guest Billy Joel. Fittingly, Murray was a guest on the final "Late Show," but he does not hold the record for most appearances.

Regis Philbin has been on the show 150 times, including a stint as a guest host while Letterman was recovering from quintuple bypass surgery in 2000. Much like Murray, you can see the friendship between Letterman and Philbin; their conversations tend to be different from the typical guest-host dynamic.

There was also that time Drew Barrymore flashed Letterman for his birthday in 1995.

Joaquin Phoenix made a memorable appearance on Letterman on Feb. 11, 2009. The actor had a full beard and seemed off. While everyone was wondering what was going on, it was only later revealed that it was all tied in to Phoenix's performance in the film "I'm Still Here."

Speaking of infamous appearances, Farrah Fawcett had her own memorable moment on "Late Show With David Letterman" in 1997.

Madonna was a guest in 1994 and Letterman's snarky introduction won him no favors with the Queen of Pop. Letterman has a tendency to push guests or barely tolerate their existence, which can lead to interesting encounters. There was plenty of swearing and awkward moments during the segment. Madonna has been a guest several times since that appearance and the two continue to have interesting -- albeit friendlier -- banter.

Going way back to 1982 and "Late Night With David Letterman," there was the slap heard around the world when pro wrestler Jerry Lawler smacked comedian Andy Kaufman.

Crispin Glover made a memorable appearance on "Late Night With David Letterman." Glover dressed up in character as a nervous and distressed version of himself; he rambled and tried to karate kick Letterman. Letterman turned to bandleader-sidekick Paul Shaffer to express his disbelief at several points during the interview.

There were also memorable interviews with Harvey Pekar, Hunter S. Thompson and Paris Hilton. Then there's the interview with filmmaker Harmony Korine in 1995 -- he was banned from the show after allegedly going through Meryl Streep's purse.

Memorable Moments

In 2009, Letterman admitted he'd had an extramarital affair with a staffer and had been caught in an extortion plot.

"Seinfeld" star Michael Richards went on "Late Show" to apologize about racist comments he had made during a comedy club appearance, but it seemed a bit insincere. Letterman quickly questioned the apology, which led to an interesting exchange.

"Late Show With David Letterman" returned to CBS after 9/11, on Sept. 20, 2001.

Memorable Sketches

What "Late Show With David Letterman" would be complete without a Top Ten?

Many of Letterman's most famous sketches were all about being absurd. First there was "Stupid Pet Tricks," and since that was such a hit, Letterman expanded the sketch to