Being a previous Whovian re-watching for diversity was extremely interesting. Upon re-watching I also have noticed the foreshadowing and clues they put in to the future start earlier than previously noticed. For example, bad wolf begins in season 1 but the Doctor and Rose don’t notice that it is following them around the universe until the middle of season 2. As early as the beginning of season 2 you notice the vote Saxon posters in the background which aren’t apart of the story until the end of season 3. In season 3 there is also the use of the Timelords heartbeat which comes into play in season 4 with the Doctor Donna and the specials after leading to the Tenth Doctors death and regeneration. In season 5 you begin to see these cracks appearing that seem to focus in on Amelia Pond, which then cause a whole issue in season 5 and lead to the grand ending which is that the crack caused by the exploding TARDIS. Another larger clue was the ‘Silence will Fall, Doctor’ this was used in season 5 for the large plot line set up of season 6.
Within other little story lines amongst the longer storyline there are also clues as to what the truth or future will bring. A prime example of this is in the episode “Utopia” they had professor Y.A.N.A. which stood for You Are Not Alone which is what the Face of Boe told the Doctor before he died. In the same episode, they also have Jack present for all he tells the Doctor which leads up to the big reveal that the Face of Boe is Jack at the end of the story; though how he made that transformation is never revealed. In the “Time of Drums” as the toclafane are invading the Master begins playing a song in which they are referred to as your future which is a clue as to what the toclafane really are. Another is the Doctors hand being cut off and falling to earth in “The Christmas Invasion” because Jack comes back into play with the hand as a Doctor tracker which also leads to the Master getting the hand and using it for his purposes. Later the hand is used at the end of season four when the Doctor gets struck by a dalek and regenerated, he used it to keep his form and syphon off the excess energy which comes into play with creating a new Doctor and the creation of the Doctor Donna.
I love seeing the different things that the writers set up whether it be for the season or for a long-term plot hidden in the background for a long-term plot line or just within an episode storyline. It is a lot of fun to see all the little things that if you hadn’t seen in the show before when watching the show because they don’t connect in your mind as an important detail. This says that the writers have an idea where the show is going and they are going to do what they can to keep the viewers interested.