The BBC has surprised fans with a special short film today, as part of the run up to the Doctor Who 50th anniversary special on November 23. In the complex mythology of the show, the mini-episode “The Night Of The Doctor” takes place during the Time War, and shows the final moments of the Eighth Doctor—Paul McGann, in what is only his second appearance as the character and first since 1996—as he attempts to rescue a female pilot crashing onto the surface of Karn. It also features the mysterious Sisterhood that interacts with the Doctor during his final moments, and references companions exclusively heard from during the show's run on radio dramas since 2001—all exceptionally rare. But for the purposes of stitching together backstory, it sets up the crucial plot point that the Eighth Doctor transforms into the War Doctor, played by John Hurt, who will be a big part of the anniversary special. And for truly dedicated fans, here's a roundup of all the short's many Easter eggs.