Pfft. The TARDIS is the true brains of the operation. She just lets her Time Lord pet *think* he's in charge.

This is obviously true! Otherwise, why is it he can't ever get to where he wants to go? The TARDIS just likes company, that's all, and that's why the Doctor is there. And also he can reach the really itchy place in her central bubble array and sometimes he hits her voom screen just right.

...Why, no, I don't secretly slash the Doctor and the TARDIS. Not at all.