10 Best Doctor Who Crossovers Ever

Continuing the BBC's tradition of releasing special crossover episodes to commemorate Doctor Who's anniversary dates, the 50th-anniversary celebration came in the form of "The Day of the Doctor." The special was simulcast in 94 countries, which earned it a Guinness World Record and several other awards.

The 77-minute special featured the 10th & 11th Doctor meeting, but they weren't alone. The episode dealt with the final days of the Time War, which saw the destruction of Gallifrey, and the end of the Time Lords and Daleks. It's a period the Doctor never talks about, and that's due to an incarnation he hoped to forget.

John Hurt showed up as the War Doctor, and it was up to him to deliver the Moment, a weapon capable of destroying both races to end the Time War. Billie Piper returned up as a manifestation of the weapon, and Tom Baker appeared as well, though he wasn't explicitly revealed to be the 4th Doctor.

The episode was created as a "love letter to the fans," and that's precisely what it was. It managed to tie up some loose ends, feature a plethora of fan-favorite characters, and introduce the forthcoming 12th Doctor. For a 50th anniversary special, it did not fail to deliver, and most fans agree, it's the best Doctor Who crossover ever made.