Doctor Who: What Happened To Every Companion?

After the cancellation of Doctor Who, the series went dark for a while. It wouldn't come back properly until 2005, but there was an attempt made earlier. A made-for-tv movie was made and aired on the BBC in 1999, featuring the only televised appearance of the ever-charmingly befuddled 8th Doctor, played by Paul McGann.

The movie only had one companion, and even then she never really leaves with him on the Tardis, though she does help him stop The Master in this movie, which is good enough for us. Grace Holloway is a cardiologist in San Francisco, who met The Doctor shortly after his regeneration into McGann. After a movie's worth of shenanigans, The Doctor offered her to come with me, since he had grown quite romantically attached to her, but Grace offered he do the same with her. The two instead chose to go their separate ways.

Now yes, there are comics and books that go more into their adventures and even featured other companions. But this is purely about the television stuff. Fortunately, since there's no conflicting accounts from what happened in those materials, whovians are free to accept it as canon if they so choose.