imagine youre a teenager and one day you decide to steal a car because it looks fast and sleek and you want to travel on the road. so you go on a trip in your stolen car and you love it so much that you dedicate your life to the road. you spend your years travelling, visiting new places and picking up hitchhikers, all in the same car you stole, which at this point has become old and run down and needs refurbishing every now and then, but you never replace it because you live in this car now and it's your home. at one point your actual house was demolished and your family members are dead. the people you've hooked up with in your car have broken up with you and gone away. youve changed many times as a person, but your shitty car has stayed the same, the one constant in your hectic life. it's the last one of its model after they stopped manifacturing it: that's how old it is. then one day, your car suddenly breaks down in the middle of the road. you go out to get help and find a lady who weirdly knows all about you. she knows all the places youve been to and the people youve gone there with. as you talk with her more, you begin to realize that, somehow, the soul of your car—the one that's sitting broken outside—has transferred into the body of a human woman. your car is alive and now speaking to you, and she remembers all the moments you two have spent together, every word youve told her when you thought you were alone, every desire and complaint youve expressed to her in the middle of the night. your car is speaking to you, and she tells you that however much you love her, she loves you equally back. that you never really stole her all those years ago because she wanted to travel with you, and she wouldn't change you for anyone else in the world. you speak with your living human car, and you realize that, hey, she's kind of funny actually, and you might be a little bit in love with her, and she might be a little bit in love with you. but the desert you're stuck in is also sentient and evil, so your human car dies in your arms in order for her soul to transfer back into the machine and drive you away. so now you're back on the road with your car the same as always, except now you know she's sentient and maybe has feelings for you, so you sometimes let go of the wheel and let her take you wherever she wants. that's what happened between the doctor and the tardis in that one episode
