Doctor Who is one of the BBC's most successful shows of all time, but before it started TV bosses were really worried no-one would like it!
Old papers dating back to the start of the sci-fi series in the 1960s also show that the Tardis and Daleks nearly didn't exist!
Producers originally wanted The Doctor to travel in an invisible machine covered in light-resistant paint.
And TV bosses said there should be absolutely no tin robots.
Apparently, BBC head of drama Sydney Newman was really angry when he found out his rule had been broken to create the Daleks - the tin-can baddies who are armed with plungers.
But he quickly changed his mind after the Daleks appeared in episode six of the first series and an extra six million viewers tuned in!
Mr Newman was right about The Doctor's time machine though.
He said producers' ideas for The Doctor to travel in something the viewers couldn't see would never work and that the character needed a vehicle that was a strong visual symbol.