Which English King had two German mistresses who were jointly known as "the Elephant and Castle"?

George I. "The Elephant" was Charlotte Sophia Kielmannsegge, Countess of Darlington; and "The Castle" Eherngard Melusina von Schulenberg, duchess of Kendall. They were so named for their remarkable stoutness and thinness, respectively. Apparently, their names were much more picturesque than their persons.

"Elephant and Castle" being a popular English pub name (probaly from the Danish Order of the Elephant) I guess the pun was just too good to pass up.

http://mistressmanifesto.blogspot.com/2013/10/king-george-i-and-his-two-mistresses.html

Eherengard (the more important of the two) was also known as "the Scarecrow", so I suppose she could have had more than one nickname.
Charlotte was also George's half-sister. What a grand time the tabloids would have had in the 18th century, compared to the Hanovers, the current royals are as boring as sedated Sunday-school teachers.

The "Rough Guide to the History of England" describes the two of them as having been jointly called "the Elephant and Castle", but on the Internet I find another story.
http://www.cercles.com/review/r15/linnane.htm

calls the thin one the "Maypole" and the fat one the "Elephant and Castle". Might be at least one instance in which the Internet source is more reliable than printed paper.

http://www.uni-mannheim.de/mateo/camenaref/cmh/cmh601.html
has a long article on the Hannoverian succession. The author claims that the story about Baroness Sophia Charlotte von Kielmannsegge (afterwards Countess of Darlington) having been George's mistress is incorrect and can be traced back to the malicious pen of the Margravine Wilhelmina of Bayreuth. The King is said to have acknowledged and honoured his half-sister as being his half-sister, and not a mistress.

Anyway the affairs of George I may have been less exciting than it seems as
[From waterford-online.ie 2005 article, no longer online]
claims (OTD-11 June 1727) that the King spent most of his evenings with Ehrengard Melusina von Schulenberg, "indulging their shared passion for ...cutting out paper pictures."
"The Maypole" or "Scarecrow" is said to have had "the proportions of a rather aged lamp-post and about as much personality". Hard to recognize a "Castle" in her.

Elephant and Castle has two possible derivations. One is that it is a contraction of the "infanta de Castille" who passed that way, and another that it was part of the arms of the Guild of Cutlers, based in that part of London, which depicted an elephant and howda (looks like a castle) arms to show the use of ivory.