I would hang out with the staff probably, I'd probably play street fighter with them, but i think I would honestly be more interested in their upcoming work and flash for NG, and that elongated color version of the poster in the NG store. I would do different things depending on how long I was staying there, like the day or just a few hours, or just stopping by to say hi or something.
Oh I would also NEED a tour because I always wonder what all of the insides of the office look like.