The Sixth Doctor had a map of Barsoom in a TARDIS storage room. One place was labelled Helium and the name John Carter was included in the caption. (COMIC: Changes)
Behind the scenes[[edit] | [edit source]]
Barsoom was the name for Mars in the Martian Series of novels by Edgar Rice Burroughs. John Carter was the protagonist of the series and Helium was a major kingdom of Barsoom.