Tarzan

Tarzan was an inhabitant of the jungles of Africa.

Behind the scenes
Graham and Valanice travelled to the jungles to return the Golden lion which Hagatha had stolen from Tarzan. After freeing the great golden lion from its chains, they took it to its jungle home and released it.

Just before the lion disappeared into the foliage, it was joined by a tall man, wearing nothing but a loincloth. Both the lion and the man roared to the heavens, the man beating his chest, and then they were gone.

Graham himself never mentioned where the jungles were located to Derek Karlavaegen, and the writer never figured out where it was.

Behind the scenes
Technically Tarzan isn't mentioned by name, but the reference is a direct reference to Tarzan of the Jungles.