And the No. 1 reason late-night television will never be the same:
David Letterman announced Thursday that he'll retire in 2015, ending a record run of hosting sleepy-time talk shows on two networks.
No more signature top-10 lists, stupid pet tricks or absurd stunts like wearing an Alka-Seltzer suit in a water tank. The man who made grouchiness funny and turned guests into bundles of nerves, wondering what he'd say next, is stepping down as host of the Late Show with David Letterman.
The gap-toothed pride of Indianapolis announced his decision Thursday afternoon while taping that night's program at New York's Ed Sullivan Theater. R.E.M. bassist Mike Mills, a guest on the show, broke the news on his Twitter account.
Letterman, who turns 67 next week, put a customarily comedic spin on the news in a released statement, using bandleader sidekick Paul Shaffer as a punchline: "What this means now, is that Paul and I can be married."
CBS chairman and CEO Leslie Moonves apparently wasn't informed of the decision until minutes before Thursday's taping.
In a statement later, Moonves noted: "(We) knew this day was getting closer, but that doesn't make the moment any less poignant for us."
Letterman visited St. Petersburg last weekend for the Grand Prix of St. Petersburg, according to his sister, Gretchen Letterman, who has worked for the Tampa Bay Times for 31 years and edits the newspaper's high school publication tb-two*. The comedian is co-owner of the Rahal Letterman Lanigan Racing team that competed.
"I couldn't be happier for him and his family," she said. "He is the hardest-working person I know, and he deserves to be able to slow down a bit and go fishing more with his 10-year-old son. And, of course, spend more time with his sister."
Letterman's decision to retire isn't surprising after 22 years at CBS. A two-year extension signed in 2013 was widely expected to be his last. The extension also enabled him to recently surpass Johnny Carson as the longest-running host in late-night TV history, counting an 11-year stint on NBC's Late Night with David Letterman.
Delaying retirement until 2015 allows Letterman to surpass his rival Jay Leno in late-night longevity on a single show. Leno retired from hosting NBC's Tonight Show in February after 22 years. Their relationship forged as rising comedians was fractured in 1992 when Leno was named Johnny Carson's Tonight Show successor, over Carson's clear preference for Letterman.
The NBC power struggle leading to that choice inspired Bill Carter's 1994 nonfiction book The Late Shift, and later an HBO movie adaptation. Reviewer Kim Campbell of the Christian Science Monitor wrote: "Carter's eye-opening book leaves the impression that NBC will be remembered more for its loss of Letterman than for its role as creator of late-night television."
Speculation now begins on Letterman's successor, entering a late-night talk show landscape growing younger with each hire.
An obvious but older candidate is Craig Ferguson, 51, host of The Late Late Show following Letterman for more than nine years. That program is produced by Worldwide Pants, a company owned by Letterman, so he could continue to profit from the 11:35 p.m. time slot.
While setting a standard for late-night comedy, not everything about Letterman's tenure has been funny.
Sexually charged jokes about Sarah Palin's oldest daughter Bristol — especially one mistakenly aimed at her younger sister — earned outrage from supporters of the former vice presidential candidate and the National Organization for Women.
For a decade, Letterman was stalked by a schizophrenic woman who eventually committed suicide. In 2009, Letterman confessed to sexual affairs with several female employees, revealed after a CBS producer attempted to extort money from him.
The late-night youth movement has taken a toll on Letterman's ratings, which trailed Leno's during much of his tenure. Since former Saturday Night Live star Jimmy Fallon, 39, took over for Leno, The Tonight Show averaged 4.3 million viewers nightly compared to 2.85 million tuning in to Late Show.
Despite career bumps, though, Letterman's late-night legacy is best summed by Moonves:
"For 21 years, David Letterman has graced our network's air in late night with wit, gravitas and brilliance unique in the history of our medium.
"During that time, Dave has given television audiences thousands of hours of comedic entertainment, the sharpest interviews in late night, and brilliant moments of candor and perspective around national events. He's also managed to keep many celebrities, politicians and executives on their toes — including me.
"There is only one David Letterman."
Steve Persall can be reached at email@example.com or (727) 893-8365. Follow @StevePersall on Twitter.