Air Bud: The first face that appeared on both of Letterman's late-night shows was that of Calvert DeForest, aka Larry "Bud" Melman.
From the top: Letterman's first Top Ten List, "Things That Almost Rhyme With Peas," was presented on Sept. 18, 1985. In 33 years, he will have presented 4,605 Top Ten Lists.
Marvelous Marv: The king of "Late Night," which aired on NBC from 1982 to '93, was sportscaster Marv Albert, with 73 appearances to his credit. Richard Lewis was the next most popular guest, with 48 appearances. Jay Leno wasn't far behind: 39 visits.
Reg-ing bull: As for Letterman's "Late Show" on CBS (1993-2015), Regis Philbin holds the title for most appearances, with 136.
Other top guests: Jack Hanna, 75; Tony Randall, 70; Marv Albert, 52.
He wears it well: On "Late Night," Letterman donned a number of different "suits." Most memorable was the "Suit of Velcro," which he first wore on Feb. 28, 1984. While wearing the suit, he ran, jumped on a trampoline and hurled himself at a Velcro wall. He — and the bit — stuck. Other "suits" include:

* Rice Krispies: He "snapped, crackled and popped" after being dunked in a large tub of milk.

* Sponges: He was dunked in a 1,000-gallon glass tank of water and tipped the scale at 500 pounds.

* Alka-Seltzer: Wearing protective goggles and an oxygen tank, he was lowered into a 1,000-gallon tank of water and his suit began to fizz and vaporize.
* Chips: Dave was lowered into a glass tank filled with 1,000 gallons of yogurt dip.

Stupid things: Two of Letterman's signature segments were Stupid Pet Tricks, which he started on his morning show in 1980, and Stupid Human Tricks, which began in 1983. There were 126 Stupid Pet Trick segments aired, and 89 Stupid Human Trick segments.

A league of his own: As of Wednesday night, there will have been 6,028 broadcasts of Letterman's late-night talk shows. That retirement is well deserved.

Regis Philbin dressed as Shrek for a 2009 “Late Show” visit.

Facts and photos provided by CBS.