Urinating Brute

On the level "The Ark", when you reach the room with sleeping Grunts after destroying the Scarab, by the door you go to through to continue farther in the level there is a Brute taking a "break" in the corner. He originally has his hands in front of him, but after a short time he will move his hands behind his head and then shake the excess urine off. After a while it will move into the main hallway. This Brute may be an Easter Egg, but its rank is still affected by the difficulty setting within the game. A marine says 'Chief, tap him out'. The gender of this voice depends on the difficulty as well.

The best way to see this is to start The Ark on Rally Point Bravo go straight and then look at the right corner of the room. If you play the whole level when 343 Guilty Spark stings the curious marine go into that room and do what is described just above.

It carries a Brute Spiker.

If you look at the walls and the floor after he is done you can see what he has left behind.

Link to the video here.