The Last of Us had several possible endings before Naughty Dog narrowed it down - but only one of those endings featured Joel breaking out into song.
Voice acting is hard work, especially on a game as character-driven as Naughty Dog's The Last of Us. The game's emotional climax was particularly tough to capture, and after several takes the cast and crew were understandably drained. So how do you raise morale after a long day of performing? If you're Neil Druckmann, creative director and mad genius, you spin the game's dark finale into a sudden, improvised musical. Obviously, since this is the end of the game, the video is riddled with spoilers.
Troy Baker and Merle Dandridge, who played Joel and Marlene respectively, are both talented singers - though the dreary script of The Last of Us doesn't really call for Broadway performances, despite Ellie's requests. Before the final take of the game's climactic scene, however, Druckmann took Dandridge aside and secretly instructed her to belt out her lines in song. Meanwhile, Baker was told nothing but "keep going, no matter what."
What's impressive is that the voice actors didn't even blink as they delivered their lines to an impromptu tune, transforming a sober scene into an inspired, borderline-uplifting act. They played the scene, straight faces all around, through to the end. This, ladies and gentlemen, is why voice acting is more than just talking into a microphone - this is talent.
Source: PlayStation Blog