So, first, a crossover.
Story:Hellmouth High Schools Don't Have Reunions
Author: Morag MacPherson
Rating: All Ages
Word Count: 16315
Author's Summary: What if "School Reunion" took place at Sunnydale High School? A BTVS crossover.
Characters/Pairings: Rose Tyler, The Doctor (10th)
Recced because: On being told that this is a "remix" of the episode "School Reunion", many people would justifiably run screaming, but this works amazingly well. Yes, there was deja-vu in a few places, since certain of the best lines from the original episode were re-used, but unlike other retellings, this really got into the spirit of the crossover, and rather than just try to map the plot of the original "School Reunion" onto the characters, it took the scenario and then let the characters run with it the way they would have if it had been an original Buffyverse story. You get all the quips and snark and unfolding of the plot, and everyone is in character. I'm particularly impressed with how the author resolved the incompatibilities between the Buffyverse and the Doctor Who universe.