The TARDIS has a vast interior but appears smaller on the outside, and is equipped with a "chameleon circuit" intended to make the machine take on the appearance of local objects as a disguise; due to a malfunction, the Doctor's TARDIS remains fixed as a blue British police box. The Doctor often finds events that pique their curiosity and tries to prevent evil forces from harming innocent people or changing history, using only ingenuity and minimal resources, such as the versatile sonic screwdriver.
The Doctor rarely travels alone and often brings one or more companions to share these adventures. These companions are usually humans, owed to the Doctor's fascination with planet Earth, which also leads to frequent collaborations with the international military task force UNIT when the Earth itself is threatened. As a Time Lord, the Doctor is centuries-old and has the ability to regenerate in case of mortal damages to the body, taking on a new appearance and personality.
The Doctor has gained numerous reoccurring enemies during their travels, including the Daleks , the Cybermen , and the Master , another renegade Time Lord. Kennedy the previous day. Discussions and plans for the programme had been in progress for a year.
The head of drama Sydney Newman was mainly responsible for developing the programme, with the first format document for the series being written by Newman along with the head of the script department later head of serials Donald Wilson and staff writer C. Writer Anthony Coburn , story editor David Whitaker and initial producer Verity Lambert also heavily contributed to the development of the series.
As originally written, the Daleks and Thals were the victims of an alien neutron bomb attack but Nation later dropped the aliens and made the Daleks the aggressors. When the script was presented to Newman and Wilson it was immediately rejected as the programme was not permitted to contain any " bug-eyed monsters ". We had a bit of a crisis of confidence because Donald [Wilson] was so adamant that we shouldn't make it.
Had we had anything else ready we would have made that. The serial introduced the eponymous aliens that would become the series' most popular monsters, and was responsible for the BBC's first merchandising boom. Falling viewing numbers, a decline in the public perception of the show and a less-prominent transmission slot saw production suspended in by Jonathan Powell , controller of BBC 1.
Philip Segal , a British expatriate who worked for Columbia Pictures ' television arm in the United States, had approached the BBC about such a venture as early as July , while the 26th series was still in production. Although the film was successful in the UK with 9. In September of that year,  BBC Television announced the in-house production of a new series after several years of attempts by BBC Worldwide to find backing for a feature film version.
No full series was broadcast in ,  although four additional specials starring David Tennant were made. In January , Moffat announced that he would step down after the finale, to be replaced by Chris Chibnall in This is similar to the continuation of Mission Impossible ,  but differs from most other series relaunches which have either been reboots for example, Battlestar Galactica  and Bionic Woman or set in the same universe as the original but in a different time period and with different characters for example, Star Trek: The Next Generation and spin-offs.
The programme has been sold to many other countries worldwide see Viewership. Public consciousness It has been claimed that the transmission of the first episode was delayed by ten minutes due to extended news coverage of the assassination of US President John F. Kennedy the previous day; in fact it went out after a delay of eighty seconds.
Morality campaigner Mary Whitehouse repeatedly complained to the BBC in the s over what she saw as the show's frightening and gory content. The electronic theme music too was perceived as eerie, novel, and frightening, at the time. A article placed this childhood juxtaposition of fear and thrill "at the center of many people's relationship with the show",  and a online vote at Digital Spy deemed the series the "scariest TV show of all time". Some notable exceptions were: The Daleks' Master Plan , which aired twelve episodes plus an earlier one-episode teaser,  " Mission to the Unknown ", featuring none of the regular cast  ; almost an entire season of seven-episode serials season 7 ; the ten-episode serial The War Games ;  and The Trial of a Time Lord , which ran for fourteen episodes albeit divided into three production codes and four narrative segments during season While the show continued to use historical settings, they were generally used as a backdrop for science fiction tales, with one exception: Black Orchid , set in s England.
This system was shortened to twelve episodes and one Christmas special following the revival's eighth series. Each series includes both standalone and multiple episodic stories, linked with a loose story arc that is resolved in the series finale.
As in the early "classic" era, each episode, whether standalone or part of a larger story, has its own title.
Occasionally, regular-series episodes will exceed the minute run time; notably, the episodes " Journey's End " from and " The Eleventh Hour " from exceeded an hour in length. Four mini-episodes, running about eight minutes each, were also produced for the , and Children in Need charity appeals, while another mini-episode was produced in for a Doctor Who-themed edition of The Proms. The 2-part story, entitled Dimensions in Time , was made in collaboration with the cast of the BBC soap-opera EastEnders and was filmed partly on the EastEnders set.
A two-part mini-episode was also produced for the edition of Comic Relief. To celebrate the 50th anniversary of the show, a special 3D episode, " The Day of the Doctor ", was broadcast in Doctor Who missing episodes Between about and , large amounts of older material stored in the BBC's various video tape and film libraries were either destroyed, [note 3] wiped , or suffered from poor storage which led to severe deterioration from broadcast quality. This included many old episodes of Doctor Who, mostly stories featuring the first two Doctors: William Hartnell and Patrick Troughton.
In , almost all episodes then made were known to exist at the BBC,  while by the practice of wiping tapes and destroying "spare" film copies had been brought to a stop. Audio versions of all of the lost episodes exist from home viewers who made tape recordings of the show. In addition to these, there are off-screen photographs made by photographer John Cura , who was hired by various production personnel to document many of their programmes during the s and s, including Doctor Who.
These have been used in fan reconstructions of the serials. These amateur reconstructions have been tolerated by the BBC, provided they are not sold for profit and are distributed as low-quality VHS copies. The BBC, in conjunction with animation studio Cosgrove Hall , reconstructed the missing episodes 1 and 4 of The Invasion , using remastered audio tracks and the comprehensive stage notes for the original filming, for the serial's DVD release in November The missing episodes of The Reign of Terror were animated by animation company Theta-Sigma, in collaboration with Big Finish , and became available for purchase in May through Amazon.
In April , Blue Peter launched a challenge to find missing Doctor Who episodes with the promise of a full-scale Dalek model as a reward. Episode 3 of The Web of Fear is still missing.