9 Best 9th Doctor Episodes
3. Father's Day
The Doctor has a select few rules when it comes to traveling with him. One of the big no no's by far is not altering your own timeline, especially big life-defining moments such as - for example - the death of a loved one. But if Rose listened to things like reason, she wouldn't be travelling with The Doctor to begin with.
When Rose asks The Doctor to take her back to 1987, when her father was killed in a hit-and-run, just so she can see the man she lost when she was a baby, she impulsively saves him instead, disrupting the flow of time and space. Now, thanks to Moffat's era, we know what happens when a time traveller is spared when they were supposed to die, but how does the time stream respond to a normal person not dying when they should?
Well, in a twist right out of a Stephen King book, giant monsters appear to gobble up everything until the anomaly is corrected. I never said it was a twist from a GOOD Stephen King book.
As silly as the idea of giant bat monsters being time's response to being messed with is, the emotion at the core of the story is always the focus and works wonderfully.