The second class of astronauts chosen by NASA, 'The New Nine', may have in fact been the 'Top Secret Ten'. At least that's what Jim Lovell and Pete Conrad wanted the Press Corps to think.
The two pranksters would intentionally let members of the press overhear them speak about Walter Frisbee, a top secret astronaut with wildly incredible talents that NASA wanted to keep hush, hush. Was he the son of a Romanian nobleman? Maybe. Was he the most fearless, talented test pilot that ever took to the skies? Definitely.
The other members of The New Nine got on-board with the joke and as reporters quizzed each one about Frisbee they'd acknowledge his existence, excuse his absence due to his mysterious, extraordinary training and say nothing else. Rumor has it the press actually started writing about Fearless Frisbee in the papers and that's when NASA pulled the plug on this little prank.
[Within the last few years an account on Twitter, Astro_Walt, has popped up with the simple bio, "Pilot and astronaut, retired." Who knows, maybe it wasn't a prank after all....]