Spoilers for end of season 1, beginning of season 2, if you haven't seen it yet.
This is my theory about how Nathan got that weird beard of his in the season 2 opener. The Petrellis express their emotions through hair.
...It was funny in my mind.
EDIT: What? Now the EmoBeard is gone! My picture is no longer relevant. D: I wasn't even done making fun of it yet!