Several characters have been recast for the upcoming Season 4 of HBO's hit medieval fantasy, "Game of Thrones," including Gregor Clegane, The Mountain, who is now played by Hafthor “Thor” Bjornsson, who recently took to Instagram to share some behind-the-scenes photos with Lena Headey.

Ser Gregor Clegane, the head of House Clegane and feared bannerman of House Lannister, was originally played by Conan Stevens in Season 1 before being replaced by Ian Whyte, who had previously played a White Walker, as Stevens went on to film "The Hobbit" and the second season of "Spartacus: Blood and Sand."

Now Gregor Clegane has been recast once more, Bjornsson tweeting back in September the good news to his fans that he had won the role for the fourth season, writing, "For all my fans! I am happy to tell you that I will be THE MOUNTAIN In season 4 In Game Of Thrones :)"

Fan responses were generally positive, as the Icelandic strongman makes for a fierce-looking Mountain. New photos of Bjornsson filming show off his shockingly massive size, especially when standig next to castmate Lena Headey, who plays Cersei Lannister, and when wearing an impressive full suit of armor.

Also recast this season is the role of Daario Naharis, a swellsword who pledged his loyalty to Daenerys Targaryen at the end of last season, the role taken over by actor Michiel Huisman after fans complained that Ed Skrein looked nothing like the character described in the books, George R. R. Martin's "A Song of Ice and Fire" series.