Nani? = What?
-chan = suffix used for children, people younger than you, or close friends.

Piro speaks:
actually, .hack and Engames are quite different. If the fact that they are part of some kind of MMPORG system makes it copying, than .hack itself is a rip from any number of game oriented stories that have come up over the years (like adventure quest, etc)
The main difference between .hack and engamges is that there is no awareness that the characters in engames are aware that they are characters. .hack takes the idea that there is no transference between the two - you act like you are a game character, not a character IN the game. In Engames, thats not the case. Pirogoeth is her OWN entity, just as largo's in game character is HIS own entity. the player just gives them will and direction. To get corny, the players are like the 'soul' or spirit side of the character, while the physical game character, in that world, is their own entity. they have no knowledge of servers and things - servers going offline are parts of their world disappearing.
I'm a firm believer in relative knowledge and 'filling in the gaps'. It's all about perception, its always different from different points of view, and different modes. Emotionally, when you are in game, you are IN game. So it makes sense that the character is :)