Ok! So! I just thought of something and it's probably already done but anyway! Casanova is the doctor, like properly the doctor! For people who don't know, before doctor who, David tennant stared as the sex god, Casanova, it's ok youtube, I recommend it, he's brilliant as usual! Anyway! At a point in the story, Jack (cas), is exciled from Italy and is forced into France. If this theory is correct then the white horse that follows the doctor around is simply the white horse in the actual movie! Following it's owner. More evidence comes from the point that out of every tennant role, Casanova talks the most like the doctor, seriously watch the movie, it's scary similar. Another point that could be made is that cas is writing a memor when he's old about all the woman he's been with and his life, the girl he's telling the story to is shocked, because he remembers them so well, even in his old age. This! Is because due to crazy Timelord memory capacity it's possible! The doctor also says he never forgets a face and every person he's met is remarkable, so if course he would remember women he's intament with! Also! When rose attacks his face with hers in the second episode of the second season and he says 'yep, still got it.' He's not referring to yes, the doctor is still attactive, cause duh, but to the time in which women threw themselfs at him! So something happened between Christmas and then and we just never knew. So, Casanova dies in the movie right? NOPE! Like the master when they go to the end of the earth, old cas finally open the watch and bam! Doctor again!