5. Jo Grant
The one companion that truly defines the Third Doctor's era is Jo Grant, played by Katy Manning. Sure, there was Sarah Jane as well, but the rapport between Jo and the Third Doctor was just amazing. Her introduction in Terror of the Autons is actually one of the most amusing little scenes. Jo tries so hard to help the Doctor, and he assumes she is the tea lady, and keeps insisting he doesn't want any tea that day. She stands there, and watches him work, and suddenly it goes off in smoke. So she quickly flies into action and gets the fire extinguisher. The Doctor gets angry instead and here we see his insults start: he calls poor Jo a ham-fisted bun vendor. Jo's good-natured personality seemed to help calm the sometimes bad-tempered Doctor, and once in awhile she would even get him laughing. I believe Jo and the Third Doctor's friendship proves there can be a solid, true friendship, that can be very close friends that doesn't have to push to borderline romance. Jo's departure really hit the Doctor hard. I suggest to the New Who fans, get a copy of The Green Death, and watch the entire episode. It's extremely good, but if you love Jo as much as everyone else does, grab a tissue.