Stephen Colbert Nearly Worked for David Letterman -- Twice

April 23, 2014 — -- Stephen Colbert almost worked for David Letterman -- twice.

Colbert, who will take over for the retiring Letterman on CBS' "Late Show" next year, discussed the duo's missed connections Tuesday, his first appearance on the program since he was selected as Letterman's replacement.

WATCH: Stephen Colbert Almost Worked for David Letterman

The Comedy Central host had his first opportunity to work for Letterman in 1986. Letterman was working at NBC then, and Colbert was accompanying his then-girlfriend to New York, where she was interviewing for an internship at Letterman's show.

Colbert was hired instead of his ex, but he turned down the job over the lack of pay.

"It's an expensive city," Colbert said. "Dave, I gotta ask ... the next job I'm taking here, that pays, right? 'Cause I already signed."

A decade later, Colbert and his writing partner, Paul Dinello, submitted material to the "Late Show" hoping to join the writing staff. Among the material was a mock Top Ten list, "Top Ten Cocktails for Santa."

One of the items was a "Scrooge Driver -- grain alcohol and regret."

But Letterman's producers took too long to get back to Colbert, and by then Comedy Central had hired Colbert and Dinello to work on the show, "Strangers with Candy."

Colbert said he's "thrilled" to be joining the program next year. Letterman also expressed enthusiasm.

"With a situation like this, Paul [Shaffer] and I have been doing this for a long time," Letterman said, "and they could have just as easily hired another boob like me, but they didn't. They hired a guy--"

"They hired a boob like me," Colbert said. "Every boob is like a snowflake, Dave. We're all unique in our own way."

The two also posed for a selfie together, a celebration of current and future "Late Show" hosts.

"Good Morning America" co-anchor Robin Roberts also appeared on the program, discussing the medical obstacles she's faced and overcome. Roberts survived breast cancer and was later diagnosed with myelodysplastic syndrome or MDS, a rare blood disorder.

WATCH: Robin Roberts Visits the "Late Show"

She underwent a bone marrow transplant in 2012, receiving donor cells from her sister, Sally Ann. Those experiences are documented in her new book, "Everybody's Got Something."

Roberts told Letterman Tuesday that she's happier and healthier than she’s ever been.

"You face the challenge and the fight in front of you, and I wouldn't change a thing," she said.

The Associated Press contributed to this report.