7. She Got Cloned
When Martha decided to leave the wonders of the TARDIS behind her at the end of Series 3, and with her experiences in dealing with a whole manner of extra-terrestrial excursions added to her glittering résumé, she decided to put her talents to good use in a more Earth-based role as UNIT's new medical officer. The Doctor's personal recommendation would've certainly worked in her favour, too! Her time aiding the military organisation turned out to be just as eventful as her former life amongst the stars - if not even more so. After a short but sweet stint in Doctor Who's spin off Torchwood, which saw her reunited with Captain Jack, she called upon the Tenth Doctor for help when Earth was invaded by the belligerent Sontarans. Things only got all the more confusing when she was subsequently cloned and her calamitous counterpart was used to assist the Sontarans in their evil bidding. The clone ultimately came through, though, and proved to be just as resourceful as the person from which it had been spawned. If nothing else, it proved that you're never alone when you've got a clone. Until that clone dies, of course, and then you're alone again.
Credit where credit's due, Martha once again handled the situation extremely well. How often do you get the chance to have a heart to heart with yourself? In fact, nothing up to this point seemed to phase her at all, until it all got to much for her during her next adventure and she ended up breaking down in a bog. Speaking of which...