When Carl Sagan said "billions" during the 13 episodes of "Cosmos: A Personal Voyage," viewers knew it. His overemphasis of the "b" in "billions" was deliberate; to make sure the word was not mistaken for "millions." Still, he never uttered the catchphrase "billions and billions."
It was Johnny Carson, host of "The Tonight Show," who cemented Sagan's relationship with "billions and billions" of galaxies. Sagan appeared as a show guest more than two dozen times, and Carson's popular impersonation of him repeating the phrase, made a lasting impression — one Sagan was never able to shake. It was copied by other comedians and satirized in a Frank Zappa song.
In Sagan's (perhaps sarcastically titled) book, "Billions and Billions," he wrote, "Oh, I said there are maybe 100 billion galaxies and 10 billion trillion stars. It's hard to talk about the Cosmos without using big numbers...But I never said 'billions and billions.' For one thing, it's too imprecise.... For a while, out of childish pique, I wouldn't utter or write the phrase even when asked to. But I've gotten over that. So, for the record, here goes: 'Billions and billions.'"