School Reunion

"School Reunion" is the third episode in the second series of the British science fiction television series Doctor Who. It first aired on BBC One on 29 April 2006. The episode's narrative takes place in England some time after the events of the 2005 episode "The Christmas Invasion", and involves the Tenth Doctor (David Tennant) reuniting with his former travelling companion Sarah Jane Smith (Elisabeth Sladen), whom the Fourth Doctor left behind in the 1976 serial The Hand of Fear. In the episode, the alien race the Krillitanes, disguising themselves as school faculty, use the minds of children to solve a theory of everything that would allow them to control time and space. The use of the Doctor's previous companions, in particular Sarah Jane and K9 (John Leeson), was first proposed in 2003 to the BBC. After the episode was produced, Elisabeth Sladen was approached by the BBC to star in a spin-off, The Sarah Jane Adventures, which also included K9 in several stories. The episode was positively reviewed, with an Appreciation Index of 85 ("Excellent"). Plot Mr Finch, the headmaster of Deffry Vale School, has been changing the school to improve the students' performance; his changes include free lunches with special chips. The Tenth Doctor is undercover as a science teacher in the school, and Rose is working undercover in the school's cafeteria. The Doctor discovers the oil in the chips has caused the students' increase in performance. Rose observes that the chip oil has an adverse effect on the other kitchen staff, who must use hazmat suits to handle it.