In “Father’s Day,” Rose wants to visit her father, Pete Tyler, on the day he dies, in order to be there for him. He died in 1987 when she was young, so he will not recognize her as an adult. The Doctor, seemingly showing off a bit, decides to let her go to him. Rose cannot go through with it at first, so the Doctor allows her to try again. Impulsively, Rose decides to leap out and save her father, rather than be there as a comfort in his death. This causes her to cross her own timeline, altering time. To paraphrase the Doctor, there’s a person alive in the universe who wasn’t alive before, and this can cause unforeseen problems in the universe. Rose befriends her father, without disclosing her true identity to him, and they meet up with Roses’ mother Jackie at a wedding.
Meanwhile, strange dragon-creatures, Reapers, are attacking the people in the vicinity of the church. Because of Rose’s meddling, time is damaged, and the creatures are like bacteria, attempting to sterilize the wound by killing everyone. The Doctor must repair the damage and return things to their right order. Eventually, Rose reveals her identity to her father, disillusioned with what her mother has always told her about her father and what she finds. Their relationship is not what her mother made it out to be. She meets her infant self (though she cannot touch her, for that would create a paradox), and even Mickey, who runs up and hugs her.
Again, the show emphasizes humanity’s greatness, with the Doctor marveling at the human condition. Humanism lies at the core of the show, yet there still remains the need for a savior, someone to rescue them from their shortcomings. Rose must repent of her mistake, reconciling with the Doctor. Soon after she does this, he comes up with a plan. He will always save the people he loves, despite their mistakes.
Rose, about the Doctor: “We’re not a couple. Why does everyone keep asking if we’re a couple?”
The Doctor to the baby Rose in 1987: “Good girl. Yes, you are. You’re not gonna bring about the end of the world now are you?”