Rat Rats were small rodents found on Earth and other planets . They were generally considered pests by human s . Polly was virtually incapacitated by her fear of rats in a 17th century jail , ( TV : " The Smugglers " ) and the Eleventh Doctor once claimed to hate rats . ( TV : " The Wedding of River Song " ) Rats were often associated with cheese . ( TV : " The Bells of Saint John " ) In the Doctor ' s TARDIS , Erimem fed Antranak dead rats from the food machine . ( AUDIO : " Nekromanteia " ) History . According to folklore , the Pied Piper rid the German town of Hamelin of its rats in exchange for twenty bags of gold in 1284 . ( COMIC : " Challenge of the Piper " , TV : " The Day of the Clown " ) In 1605 , the drains near the Houses of Parliament in London were infested with rats . The plotter Thomas Percy was disgusted by them . ( GAME : " The Gunpowder Plot " ) In the 14th century , flea s on rats carried the bubonic plague throughout Europe . Terileptil prisoners who found themselves near London in 1666 exploited this to engineer a new plague variant that was injected into the rats . This plague was prevented by the Fifth Doctor . ( TV : " The Visitation " ) In Paris in July 1794 , Susan was frightened by the rats she saw in the jail cell in which she and Barbara Wright were imprisoned . ( TV : " The Reign of Terror " ) While escaping the Squall in 1910 , Amy Pond and Rory Williams entered the London sewers . The sewers were infested with rats , to Amy ' s horror . ( PROSE : " Paradox Lost " ) During the First World War , some rats were modified by the Dalek s as part of the Dalek Project . A cyborg rat saw Corporal Edward Anderson running through a trench . The rat followed him and was killed . Another rat observed the Eleventh Doctor and his companion s running through the trench before going to Hellcombe Factory . After the Daleks were defeated , a surviving modified rat saw the Doctor and Angela Todd drinking tea . In 2017 , a rat crawled on a nearly damaged Dalek as its eyestalk glowed blue , indicating that the Dalek was still alive . ( COMIC : " The Dalek Project " ) During the Spanish Civil War , the trenches were often infested with rats . George Orwell found them the most distressing factor of trench warfare . ( PROSE : " History 101 " ) In the 1970s , Arthur Linwood , a medical student with a morbid fear of rats , was killed at Stangmoor Prison when the Keller Machine turned his fear against him . His fear was so great that rat bites and scratches manifested on his face and neck . ( TV : " The Mind of Evil " ) In the cellar of a Spanish hacienda in the 1980s , Shockeye of the Quawncing Grig caught a rat , broke its neck and began to devour it raw . He was displeased with the taste , hypothesising it might be more tolerable smoke - dried . ( TV : " The Two Doctors " ) In 2007 , undercover Krillitane at Deffry Vale High School freeze - dried rats to eat later . Mickey Smith let out a scream when accidentally discovering this supply . ( TV : " School Reunion " ) The brother of Gwen Cooper ' s friend Janice had a pet rat named Fang . ( AUDIO : " Love Rat " ) The Fifth Doctor found some rats in Striker ' s Edwardian yacht . ( TV : " Enlightenment " ) In 2050 , the Space - Time Manipulator released a couple of black rats in Gryffen Manor , frightening Darius Pike . While these rats were otherwise identical to normal rats , they multiplied once every ten seconds . ( TV : " Liberation " ) Paradise Towers had a rat population after it fell into ruin . ( TV : " Paradise Towers " ) Following the 22nd century Dalek invasion , the rat population in England surged , likely because basic services had been discontinued . Prices for cat s went through the roof . ( PROSE : " Legacy of the Daleks " ) Rats inhabited the alleyways of the colony planet Vourakis 3 . ( COMIC : " Pirates of Vourakis " ) By the 30th century , all wild animals and plants were extinct except for humans and rats . ( PROSE : " Just War " ) Rats were a common sight in the filthy Earth colony on Lebenswelt . One rat tried to bite Anji Kapoor ' s nose . ( PROSE : " The Book of the Still " ) At some point in the 52nd century , rats would sneak into the Seventh Transept where they were eaten by the skulls of the headless monk s . ( TV : " The Wedding of River Song " ) On the planet Gyros , the Gyro s destroyed rats which tried to eat the food the robots had harvested and stored . ( COMIC : " The Gyros Injustice " ) Rats existed on Skaro until the latter stages of the Thousand Year War . ( AUDIO : " Davros " , " Corruption " ) The Steggosian s were wiped out by a plague they had caught from rats . ( PROSE : " The Eyeless " ) In experiments . Rats were used in experiments as test subjects , since they could be bred quickly . In the late 19th century , Magnus Greel created giant rat s and set them loose in the London sewers to guard his underground laboratory . ( TV : " The Talons of Weng - Chiang " ) According to Sarah Jane Smith , dead rats were used as a teaching tool in schools , although this practice had been discontinued by Rose Tyler ' s time . ( TV : " School Reunion " ) Richard Harries used a pair of sibling rats in his experiments into shared brain waves . The actions one rat learnt could be performed by the other . The pair had a collective memory . Cuthbert Simpson implanted them with nano - cam s and set them free , using them to watch the residents of Banquo Manor . After Simpson was blinded , he relied on the rats to allow him to see and kept them on his person . ( PROSE : " The Banquo Legacy " ) A lab rat was used by Owen Harper to demonstrate to the Torchwood Three team the ultimately lethal effects of the " Sex Gas " on its host . The gas would cause the victim to explode , which proved to be no different with the rat . ( TV : " Day One " )