Memory Lane

Gonzo once sang '"Memory Lane" on The Muppet Show, accompanied by Rowlf on the piano. Though it aired in the 1970s, the Sixth Doctor recalled that the song itself had originated before then.

Emily Chaudhry was angry at Will for playing the song during a World War II air raid, but the Doctor assured her that Gonzo would not destroy the timelines. (PROSE: Incongruous Details)

Behind the scenes
Indeed, as the Doctor tells Emily, "Memory Lane" was not a Muppet original, and was first written by.