Stern's not the only one. When Letterman was nearly on death's doorstep with a severely constricted heart and quintuple by-pass surgery, his loyal guests, including Barrymore and Roberts, introduced re-runs of the show.
When Roberts made her return to the limelight this spring while promoting her film "Duplicity," she stopped by Letterman's set. And, as she has done before, Roberts teased Letterman about his unwed status with his longtime girlfriend Regina Lasko and mother of his son Harry Joseph. Is it just coincidence that he tied the knot with Lasko two days later?
One guest it took Letterman 16 years to woo to his couch and a decided Leno loyalist was Oprah Winfrey.
Winfrey first appeared on "The Tonight Show" in 1985 when Johnny Carson was still king and before she was talk-show queen.
She got Carson's attention for hosting "AM Chicago" a local talk show that was beating Phil Donahue. As Winfrey's star grew brighter over the years, she returned many times to the "Tonight Show" couch, but seemed to snub Letterman's invitations -- leading to rumors that there was a feud between Winfrey and Letterman.
His much-maligned joke when he was the Academy Awards host in 1995 -- the awkward "Oprah, Uma. Uma, Oprah" introduction -- didn't help. Nor did making Winfrey the frequent target of jokes on his show. In 2003, Winfrey told Time magazine she wouldn't go on his show because she was "completely uncomfortable" with the jokes.
But two years later, in a massive buildup to the show, Winfrey appeared on Letterman's stage ready to bury the hatchet, though both wondered how the supposed feud started in the first place.
"Could you tell me please what has transpired?" Winfrey asked Letterman during the show. "I have never for a moment had a feud with you."
Still, Winfrey has shown a clear preference for Leno, as has comedian Jerry Seinfeld, who recently advised Leno's successor: "The 'Tonight Show' should always feel like the headquarters for show business."
Maybe that's why some stars prefer it.