4. Most Series Resist The Urge To Kill Of The Titular Character In The First 10 Minutes Of The Season Opener...
In the promotional material for The Impossible Astronaut, they made quite a big deal out of the fact that one of our four beloved lead characters* was going to die in the season opener. And we all assumed that it would probably just be Rory again, since we were sort of used to that by that stage. It was therefore with more than a little mild surprise that we saw The Doctor gunned down by a spaceman who appeared to live in a middle-sized lake in Utah (as one does) and then verified dead by two independent sources. Of course we all knew that something would happen to reverse it before the end of the episode, since there was the slight detail of them having to make 12 more episodes that year with him in them. Which is why I personally enjoyed the twist of then having the 200-odd year younger Doctor turn up and realizing that the rest of the season was going to be building up to where we saw the Doctor at the very beginning. Obviously nobody thought that they were actually going to kill him off, but it provided a nice shape for the season.
* Or 'Three Beloved lead characters and River", if you're of that school of thought. Personally I like her.