Unlike some of O'Brien's previous guests on the show, neither Headey nor Dinklage — who play Cersei Lannister and Tyrion Lannister — have any idea of how to play the game. At one point toward the beginning of the video, Dinklage even asks how to use the Xbox One controller he's been given.
They spend most of the video scrolling through various characters from the game in the character selection screen, offering their various opinions on each, including Junkrat, Lucia and Widowmaker. The rest of the time, they're tasked with taking on different missions and defending objectives, but like most Clueless Gamer segments, end up just running around and wreaking havoc.
Overwatch was finally released last night on PC, PlayStation 4 and Xbox One. A comprehensive guide to choosing your character can be found here.