Rudolph the Red-Nosed Reindeer
From Tardis Wiki, the free Doctor Who reference
Rudolph the Red-Nosed Reindeer was a popular Christmas song on the planet Earth, originating in the mid-1940s. It became a standard in 1948 when it was recorded by American singer Gene Autry and subsequently inspired many aspects of the Santa Claus legend.
A rock and roll version of the song was popular on Earth in the early 21st century (DW: The Christmas Invasion, Turn Left)
Behind the scenes
The same recording of the song is used for both episodes, but the performers are not credited.