Cliff Richard was a popular musician and actor on Earth in the 20th and 21st centuries.
The Shadows were a band fronted by Cliff Richard. While studying at Coal Hill School, Susan Foreman said she was not a fan of them. (PROSE: Time and Relative)
Rose Tyler and her mother, Jackie, watched Cliff Richard movies "every bank holiday Monday". Rose told the Tenth Doctor she picked up 1950s slang from these movies. The Doctor responded, somewhat derisively, "I knew your mum would be a Cliff fan." (TV: The Idiot's Lantern)
Hugh and Janet had Cliff records in their collection. (PROSE: Cat's Cradle: Witch Mark)