ABBA

ABBA were a Swedish band popular during at least the 1970s. They were of especial interest to the Tenth Doctor and Torchwood Three. Shortly after his regeneration, the Tenth Doctor dropped Rose Tyler off at a 1979 ABBA concert in Wembley Stadium. (DW: Attack of the Graske)

Later, the Doctor used his psychic paper at another concert to convince security that he and Donna Noble were Björn and Frida, two members of the band itself. (NSA: Dead Air)

In college, Gwen Cooper found out a number of her boyfriends were interested in ABBA and other men. Connecting the two, she was thankful that Rhys Williams never liked the band. Conversely, Ianto Jones liked their music in general but hated the song "Dancing Queen". (TWN: The Twilight Streets)

Jack Harkness remembered them winning the Eurovision Song Contest. (BBCR: The Dead Line)

Flip Jackson had never possessed a solid grasp of history and her only knowledge of the Battle of Waterloo on 18 June 1815 came from ABBA's song "Waterloo". Upon meeting Napoléon Bonaparte only hours before the battle was to take place, she told him of its outcome by quoting the song's opening lyric: "At Waterloo, Napoléon did surrender." (BFA: The Curse of Davros)

Behind the scenes

 * Two members of ABBA were interested in producing a musical based on Torchwood.