"A Game of Thrones," the first book in George R. R. Martin's popular fantasy series, was published in 1996. Fifteen years and four books later, HBO picked the massive story to become a series on their channel. The show was an immediate success due to its existing fan base from the novels and plenty of viewers experiencing the excitement for the first time.
In the four and a half years since the series premiered, "Game of Thrones" has established itself as a cultural phenomenon in a way few other series have. The show's theme, which was composed by Ramin Djawadi, has become hugely iconic as well, even being covered by popular bands like Chvrches. Having popular bands cover your theme song is one thing, but becoming so popular that the Queen's Guards pay tribute puts "Game of Thrones" in a class of its own.