The Doctor

The Doctor is a Time Lord, a time traveling alien from the planet Gallifrey, and is the main protagonist of the British Television show, Doctor Who. Using his Tardis, (Time and Relative Dimensions in Space), that he stole from Gallifrey. He is the last known living Time Lord with the exception of the Master. His true name is unknown, but his title is known as the Doctor, and it is even said that he is the reason why the word 'doctor' also means 'healer'. He travels across the stars with companions, usually humans, because they help him realize and see beauty in things that he normally wouldn't have seen. ''"You make all of space and time your backyard, and what do you have?" - Eleven. ''   He has been played by William Hartnell, Patrick Troughton, Jon Pertwee, Tom Baker, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann, John Hurt, Christopher Eccleston, David Tennant, Matt Smith, and Peter Capaldi.

Canon Plotline
The Doctor has had many companions. The First Doctor has had a total of twelve. He started with his granddaughter, Susan, and her two schoolteachers, Barbara Wright and Ian Chesterton. Along the way, he has let many go and gained many more, including Vicki, Steven Taylor, Katarina, Sara Kingdom, Dodo Chaplet, Polly, and Ben Jackson. Of all of these, the only one that has not been human is the Doctor's granddaughter, Susan. The First Doctor was very condescending to his human companions, and was a mysterious and ruthless figure. Only after traveling with human for a good while, he noticed their worth and appreciated his companions, becoming the grandfatherly-figure most knew him as.

The Second Doctor has had a total of six companions. Two of them, Polly and Ben Jackson, experienced him in both his First and Second Regenerations. Following the previous two, we were introduced to some new companions, named Jamie McCrimmon, Victoria Waterfield, Zoe Heriot, and Brigadier Lethbridge-Stewart. The Brigadier is a very prominent reoccuring character, showing up through the series all the way to the Seventh Doctor's era. Two would often manipulate people for the greater good and like a bumbling fool in order to have people underestimate his abilities. He's been nicknamed the "Cosmic Hobo", because his Second Regeneration was so much more childlike and scruffy than his First.

The Third Doctor had three companions: Liz Shaw, Jo Grant, and Sara Jane Smith.