Task: Explanation
Input (English): Gregor Clegane, nicknamed "The Mountain That Rides" or simply "The Mountain", is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones". In the books, the character is initially introduced in 1996's "A Game of Thrones". He subsequently appeared in "A Clash of Kings" (1998), "A Storm of Swords" (2000) and in "A Dance with Dragons" (2011). Question: Hafþór Júlíus Björnsson plays an HBO character who first appears in book form in what year? Answer: 1996
Output (English):  In the books, the character is initially introduced in 1996s A Game of Thrones.