<P> The episode "Hide" (2013) revealed that the Doctor's TARDIS is capable of operating autonomously; in the storyline, Clara convinces the ship, simply by speaking to her, to enter a pocket universe to rescue the imperiled Doctor . </P> <P> The undisguised appearance of a Type 40 TARDIS' exterior is a silver - grey cylinder only slightly larger than a police box . Its door is recessed and slides to open . This default state has appeared in 2013's "The Name of the Doctor", which depicts the TARDIS' original theft by the Doctor . </P> <P> Although a TARDIS is supposed to blend inconspicuously into whatever environment it turns up in, the Doctor's TARDIS retains the shape of a police box because of a fault that occurred in the first Doctor Who serial, An Unearthly Child (1963). The ability to alter its appearance was first mentioned in the second episode of the series, where the First Doctor and Susan noted the unit was malfunctioning . ("It's still a police box! Why hasn't it changed?") It was first given a general term of a "camouflage unit" in The Time Meddler (1965). The name "chameleon circuit" was first used in the 1975 Target Books novelisation of The Terror of the Autons, and eventually mentioned on screen in Logopolis (1981). The circuit was called a "cloaking device" by the Eighth Doctor in the television movie Doctor Who (1996), and again a "chameleon circuit" in the 2005 series episode "Boom Town". </P> <P> The Doctor attempts to repair the circuit in Logopolis, to disastrous results . He tries again in Attack of the Cybermen (1985), but the successful transformations of the TARDIS into the shape of a pipe organ, a painted Welsh dresser (much to the amusement of Perpurgilliam "Peri" Brown and the Sixth Doctor's annoyance) and an elaborate gateway ended with a return to the police box shape . The circuit was also repaired during the Virgin New Adventures novels, but again the TARDIS' shape was eventually restored to a police box shape . In "Boom Town", the Ninth Doctor implies that he had stopped trying to fix the circuit quite some time ago because he had become rather fond of the police box shape--a claim the Eighth Doctor makes in the 1996 television movie . </P>

When did the tardis get stuck as a police box
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