Piper Maru

Conception of the episode originated in two visual images series creator Chris Carter had wanted to include in a script "since the beginning of the show".[3] The first of these was that of a deep-sea diver finding a still-living pilot trapped in the wreckage of a World War II-era fighter plane; and the second was that of a black-and-white flashback taking place in a submarine.[4] Director Rob Bowman shared with Carter his experiences diving, feeling that an episode based on finding "something creepy" underwater would be a good idea.[5] Carter also wanted the episode to feature the re-emergence of the "MJ documents" last seen in the earlier "Paper Clip".[3]

Frank Spotnitz began working on the episode immediately after writing the earlier third-season episode "731", fleshing out the rest of the concept while on a flight out of Minneapolis. Spotnitz ended up writing his ideas on a magazine, not having brought paper with him, and included in his outline the investigation of Scully's sister's murder and the reintroduction of Alex Krycek.[6] The title of the episode is a reference to the first and middle name of Gillian Anderson's daughter, who had been born during the production of the second season. The name Gauthier, used for the French diver and his wife, was a reference to special effects producer David Gauthier.[7]

A WWII-era P-51 Mustang. A plane of this model is the source of the black oil in "Piper Maru".

The episode's cold open was filmed in a water tank, using a replica P-51 Mustang plane which had been designed by the art director.[5] Bowman also needed to direct a scene in which Gillian Anderson would react to a memory of playing with her sister as a child; the scene involved digitally compositing the children playing into Anderson's footage. Bowman asked Anderson to act towards a tree as though it were her sister, later telling her "I'm going to tell everybody I can that you just did that great reaction to a tree".[8] Bowman also reshot the episode's ending, as originally Duchovny and Lea were to walk past the camera and continue off-screen. Feeling this was not effective, he replaced this with a walking shot which continued straight towards and into the camera, noting that "Nick will jump in front of a truck if he think it will make a scene better".[8]

The on-screen appearances of the black oil were achieved through visual effects, with the shimmering oil effect being digitally placed over the actors' corneas in post-production. The crew went through various iterations to find the two "right" types of fluids. According to physical effects crewman David Gauthier, they used a mix of oil and acetone, which he believed gave the substance a more globular look.[9] Special effects technician Mat Beck was able to digitally bend the oil effect around the shape of the actors' eyes.[10]

The man in the plane in the teaser, Robert Maier, worked as a construction coordinator on the show,[11] and felt that his part in the episode fulfilled a "life-long dream" of working as a stuntman.[10] Nicholas Lea's name was purposely left until the ending credits in order to preserve the sense of surprise.[12]

"Piper Maru" premiered on the Fox network on February 9, 1996, and was first broadcast in the United Kingdom on BBC Two on November 27, 1996.[14] The episode earned a Nielsen household rating of 10.6 with an 18 share, meaning that roughly 10.6 percent of all television-equipped households, and 18 percent of households watching television, were tuned in to the episode.[15] A total of 16.44 million viewers watched this episode during its original airing.[15]

"Piper Maru" received positive reviews from critics. In an overview of the third season in Entertainment Weekly, the episode was rated an A. The review described "Piper Maru" as featuring "a tough and sentimental Scully", noting that "action-packed detective work by Mulder enhance[s] an already crackling scenario."[16] Reviewer Emily VanDerWerff of The A.V. Club gave the episode an A and wrote positively of the unfolding mythology, noting that the "great thing about "Piper Maru" is that it still belongs to the period of time when the mythology episodes were exposing us to more pieces of the puzzle, fitting in various things that we were meant to incorporate into the whole. This is the first time we meet the black oil, but it's obvious that others know all about it".[13] Critical Myth's John Keegan gave the episode eight out of ten, and complimented the introduction of the black oil, writing "this episode is a good introduction to the black oil virus, providing a bridge from the mythology elements earlier in the season to the larger scope of the conspiracy to be revealed."[17] Nick De Semlyen and James White of Empire named it the sixth "greatest" episode of the series, describing it as "thrilling", "pacey" and "balanced".[18]

The introduction of the sentient black oil in this episode has also been met with positive criticism. The oil has been described as "the most original and frightening creation of The X-Files' mythology",[13] as "one of the best parts of the show"[18] and has been listed as number two on Den of Geek's "Top 10 X-Files Baddies" countdown, where it was described as "a central part" of the series' mythology.[19]

Gillian Anderson considered the episode an emotionally difficult one, saying "Piper Maru was challenging. There was something about it – having to pull from the past ... how it brought the present and the past together. It was just good to play."[20] Director Kim Manners complimented Anderson's performance, stating "you look at season one and look at season three and that girl exploded as an actress in terms of talent and capability."[21] The 2004 film Alien vs. Predator featured an icebreaker named the Piper Maru, the naming of the ship being a nod to this episode.[22]