After fellow Second City alumnus Stephen Colbert succeeded David Letterman as the host of the CBS series Late Show, Stack left Conan, and returned to New York to take a job on the Late Show writing staff. He voices the characters of "Cartoon Donald Trump", "God," and "The Ghost of Abraham Lincoln" on the show.

After graduating as valedictorian in 1981, O'Brien entered Harvard University. ... He concentrated in History & Literature, and graduated magna cum laude in 1985.

Brian Stack is the voice of Wikibear in Conan.

Stephen Colbert has expanded the circle of people helping to make the ultimate decision about what the funniest things are for him to say each night on CBS' “Late Show.” Three writers/producers who have been with Colbert for years will get new duties at his late-night program.