15 Best Companions In Doctor Who History
5. Jo Grant (Katy Manning)
When Jo first appeared at UNIT HQ as The Third Doctor's new lab assistant in Terror of the Autons, it didn't look good.
Jo's happy, bubblegum nature clashed with the tetchy Doctor but as time went on, they became close. Jo trained in escapology which came in handy the several times the pair were captured by the Master or other ne'er-do-wells.
Moreover, Jo matured immensely throughout her TARDIS travels, learning from the Doctor and eventually becoming able to hold her own. Conversely, she softened the Doctor's irascible nature. By the time she decided to leave him to marry eco-warrior scientist Cliff Jones in The Green Death, it was a very sad Doctor that sneaked out of the engagement party, apparently with something in his eye, as he drove back to UNIT.
Jo later appeared in The Sarah Jane Adventures, by which time she was a grandmother. Speaking of Sarah Jane...