Real talk though The Doctor and Bill have my all time favorite relationship backstory though I mean come on
Every other companion has had to prove themselves in some way thanks to some wacky circumstance that coincidentally happened when they were nearby, before the Doctor would even give them the time of day. Even Rose was annoying to him at first and he told her to leave him alone and forget him.
And then there’s Bill who the Doctor notices sneaking into college lectures where she doesn’t belong and he thinks “I don’t know who that is but I’m her dad now”