6. Matt Smith
Matt Smith played the Eleventh Doctor, the incarnation that came just before the current one played by Peter Capaldi. His manic portrayal of everyone's favorite Time Lord was very popular and, despite being the youngest actor to ever take on the role (at age 26), he managed to create a character that seemed both young and old at the same time -- an ideal Doctor.
His character's trademark bow tie and obsession with hats were hallmarks of his style.
7. Peter Capaldi
A popular Scottish thespian, known primarily for his foul-mouthed character in the British comedy The Thick of It, Peter Capaldi took over as the Twelfth Doctor in August 2014. Capaldi's darker take on the role is in stark contrast to the charming and playful Doctors in recent incarnations -- now the character is blunt, to the point, and even a little mean.
The Doctor always likes to have a company to bring along on his adventures across space and time, and fans refer to them as "companions." Though the show tends to cast young, good-looking women in the role of companion, we've also seen men, married couples, androids, and even a robot dog traveling in the TARDIS.
Eventually, however, all of his companions leave him -- some outgrow adventuring, some run off to get married, some die, and some wind up in fates even worse than death... which leaves the Doctor as a rather lonely figure. He doesn't talk very much about his companions, regardless of their fate.
9. Jenna Coleman
The current companion is Clara Oswald, played by Jenna Coleman, who was introduced during the run of Matt Smith's Eleventh Doctor. Initially her only role was largely to follow along and get captured by the bad guys, but with Capaldi's Doctor she is starting to come into her own as smart, independent woman who questions the Doctor as much as helps him. Rumor has it that Coleman is leaving the show at the end of the year, which opens the door open for a new companion next season.