This article is from the alt.usage.english FAQ, by Mark Israel email@example.com with numerous contributions by others.
Carl Sagan (1934-1996), in his last book "Billions & Billions"
(Random House, 1997, ISBN 0-679-41160-7), admitted that in the
TV series "Cosmos", first aired in 1980, he "pronounced 'billions'
with a fairly plosive 'b'" to distinguish it from "millions". But
he asserted that he never used the phrase "billions and billions"
in that show, and that the public association of him with that
phrase is due to a parody that Johnny Carson did of Sagan on "The