2. Lisa Simpson (The Simpsons)
Intelligent beyond her years, Lisa Simpson would make a great little companion for the Doctor. Always intrigued by technology and all things sophisticated, she would find the man and his machine too tempting a proposition to turn down if he offered her the chance to join him in the TARDIS. She's bright, resourceful and keen to see the world - so why not the universe? I think the Doctor would be highly impressed by her keen observations and her maturity and he would enjoy her company immensely. Perhaps a little bit raw when it comes to battling otherworldly evil (understatement of the year right there), she's not totally unaccustomed to risk, having solved various mysteries and encountered evil-doers like Sideshow Bob.