So far, there has been a crack right at the end in every episode, The eleventh hour
The beast bellow
and Victory of the daleks
I think this has all got to do with Amelia Pond, In the eleventh hour there is a crack in Amelias bedroom wall, that all links to the beast bellow when Amy presses the forget button and at the end of the episode there is a purple crack on the Starship, that links to victory of the daleks when Amy forgets about the daleks invading the earth and the 26 planets in the sky because Amy presses the forget button in thew beat bellow, at the end of the episode the TARDIS fades away to reveal a flag, next to the flag is a white crack in the wall!