So, this is what the cast gets up to in their downtime. More and more videos of the actors messing around on set have been surfacing and they always seem to be having way too much fun. This song, in particular, is a fast paced version of "Yellow Bird" by Brothers Four with the addition of "Be happy like me!". If anything were to balance out all the death and war in this show, it's definitely Rory McCann's rendition.