Here's a music video suggesting a crossover between 'Doctor Who' and 'The Vampire Diaries':
I have no problem with this at all - if it takes place in some alternate TV dimension. As for Earth Prime-Time, perhaps it did take place during that two hundred year gap before the Doctor returned to Amy and Rory in "The Impossible Astronaut".
But I am not familiar with the details of 'The Vampire Diaries' enough to know how this could fit into Caroline's life. Besides which, all of these scenes are locked into their original use and shouldn't be repeated......