5. The Master Was Originally Intended To Be The Doctors Brother
In 1984, with Peter Davison leaving, a story was conceived called Planet of Fire in which The Master would be killed off, and in his last dying moments, The Master would plead with The Doctor to save him, saying:
"Doctor, help me! I'll give you anything in creation! Would you show no mercy to your own brother!"
However, John Nathan Turner, anticipated some fan backlash from this and so the last word brother was cut. Subsequently, The Master gave us instead a tantalising idea about what connection The Doctor and The Master have. Incidentally, Russell T Davies made a direct joke to the idea of the two Timelords being brothers - in The Sound of Drums, Martha Jones asks The Doctor if The Master is his evil brother to which The Doctor responds You've been watching too much TV!