Test yourself! Take this Dark Water Quiz | The Series (2005-)

Answer: traffic accident

Danny is talking on the phone with Clara when he is hit by a car while crossing the street. Clara has just confessed to Danny that she loves him, and she is prepared to tell him the rest of her Doctor secrets.
After Danny is killed. a heartbroken Clara demands that the Doctor bend the laws of time in order to save him.

Answer: Volcanic planet

The Doctor and Clara are on a volcano planet, where Clara attempts to blackmail the Doctor into saving Danny. She throws the keys to the TARDIS into lava, the only thing that will destroy a TARDIS key apparently. The Doctor then reveals the volcano planet is a hologram, as he was testing to see how far Clara would go to save Danny.
If you want a forest planet, you have to watch the previous episode "In the Forest of the Night".

Answer: Mobile Intelligence Systems Interface

MISI is the Mobile Intelligence Systems Interface. This week, we finally get to see Missy for more than a few moments. MISI greets the Doctor with a rather dramatic kiss, calling it the "greeting information package." When Missy offers Clara the greeting package, she replies "No thanks, I'm good." Missy (or MISI) is played by Michelle Gomez.

She has been acting in film and television since 1992. Gomez is probably best known for her television work, in programs such as "The Book Group" (2002-2003), "Green Wing" (2004-2006) and "Bad Education" (2012-2013).

Her first appearance on "Doctor Who" was in the season eight opener "Deep Breath".

Answer: 3W

3W stands for three words, those words being "Don't cremate me." Apparently the dead can feel what happens to their old bodies even after death, and so cremation would be a fairly awful fate.
3M is Minnesota Mining and Manufacturing, a real company. 3D is short for three dimensional. 3X is either triple extra large or very graphic adult motion pictures.

Answer: Young boy

Danny has several flashbacks to his time as a soldier in Afghanistan. He killed a young boy during combat, and the boy came to see Danny. He didn't really say anything, just looked at Danny with an accusing gaze. There have been references to Danny's time as a soldier in several episodes, but "Dark Water" was the first time we actually saw him in combat.

Answer: Doctor Chang

Doctor Chang was the helpful fellow in the mausoleum filled with "fish tanks." He explained the secrets of the afterlife to the Doctor and Clara, and helped Clara communicate with Danny. Chang has a fairly short role, as Missy vaporizes him. When Missy mentions the doctor, the Doctor actually asks "Doctor Who?"
Seb is Missy's other assistant. He spends much of his time during "Dark Water" trying to adjust Danny to the afterlife.
Andrew Leung played Chang. Leung is fairly new to acting, starting in 2011. His biggest role before "Doctor Who" was in the 2014 film "Lilting".

Answer: Cybermen

The Dark Water is concealing the fact that the skeletons are in fact Cybermen. Missy has been using Time Lord technology to transfer the minds of the deceased into cyber-bodies, which she stores in the tanks in the mausoleum. At the end of "Dark Water" hundreds of Cybermen were marching into the streets of London.
Cybermen are one of the oldest enemies of the Doctor, dating all the way to the time of the First Doctor. They come from Mondas, a twin planet of Earth. They were originally a humanoid species who gradually replaced their organic parts with cybernetic replacements, until the Cybermen finally eliminated all traces of humanity including emotions.

Answer: Saint Paul's Cathedral

The Doctor and Missy are standing outside of Saint Paul's. As the Doctor tries to warn the crowd, squads of Cybermen are marching out of the church. This shot is an homage to a very similar shot from the 1968 episode "The Invasion".
Saint Paul's has been the site of a church since 604 AD. The current cathedral was built by Sir Christopher Wren between 1670 and 1708, after the previous church had been destroyed in the Great Fire of London. It is one of London's most prominent buildings, a major tourist attraction, and contains quite elaborate art.
The Shard is London's first skyscraper over 1000 feet; when it was completed it was the tallest building in the European Union. The building plays a major role in the series seven episode "The Bells of Saint John".

Answer: The Master

At the end of "Dark Water" Missy reveals that her name is really short for mistress. "I can't call myself The Master, can I?"
The Master is the Doctor's most persistent Time Lord nemesis. Roger Delgado originated the role and was a regular guest from 1971 to 1973. The Master has fought against almost every Doctor, starting with the Third Doctor (Jon Pertwee). Michelle Gomez is the eighth actor to portray The Master.
The Rani was a renegade Time Lady who fought against the Sixth and Seventh Doctors. She was played by Kate O'Mara.
The Valeyard is a future evil incarnation of the Doctor. He was first seen during Season 23 of the original "Doctor Who" story arc "Trial of a Time Lord."
The Meddling Monk was the earliest Time Lord villain, fighting against the First Doctor in "The Time Meddler" (1965) and "The Dalek's Master Plan" (1966).

Answer: Rachel Talalay

Rachel Talalay was the director of both "Dark Water" and "Death in Heaven". Talalay has experience working on surreal films - she started out as an assistant for John Waters in the early 1980s. She worked on several "Nightmare on Elm Street" films and is the only woman to direct a film in the series, "Freddy's Dead: The Final Nightmare" (1991). Talalay has worked in television since 1995.
Steve Moffat wrote "Dark Water". It is the first half of a two part season finale that ends with "Death in Heaven". Moffat has been the show-runner for "Doctor Who" since the start of 2010, and he has managed series five, six, seven and eight, including the 50th Anniversary special. Moffat has written many of the best episodes of the new "Doctor Who" including "Blink" and the entire River Song story arc.
Nicholas Briggs is the voice of both the Cybermen and the Daleks. He has been doing voice work for "Doctor Who" since the restart in 2005.
Joan Blackham was the woman who picked up Danny's phone. Blackham is a veteran actress, starting in 1977. She has appeared in many television shows as well as films such as "Bridget Jones Diary" (2001).