When you get there you'll want to talk to him, make him pity the fool. And in return you'll get a five Mohawk Grenades that let you make others wear a Night Elf Mohawk mask. You can get more grenades once your five are all used up.
There is a 50 minute buff called "Mohawked" with the flavor text of "You pity the fool" that gets placed on you when you wear the mask. You can right click the debuff to remove it.
Check out the gallery below for images from this little Monday afternoon surprise. And just for kicks, the original Mr. T WoW commercial after the break. When you watch the commercial again, note how Mr. T's in-game self looks exactly like his character does in the commercial, quite neat!
Update: There is now an FAQ on the Night Elf Mohawk, which is reproduced after the break.