The games in the Borderlands series has been celebrated for their inclusion of references and easter eggs, and developer 2K Australia (with help from Gearbox) would not settle for anything less with the newly released Borderlands: The Pre-Sequel.
With this in mind they created a rather complex easter egg around a mysterious character named Nel, a charachter that will only reveal himself to fight you if you call him a dick.
That's right, collecting a bunch of letters (well, 4 really) and arranging them is the "correct" order is the only way to lure him out, and perhaps earn you some unique loot. It's all there in this video from Youtube user Prestige'r MadLuigi.
Not Nel, just a robot...