Final Battle Adventure: Online is a (fictional) game that's played by characters in Namir Deiter and You Say it First. It's mentioned prominently here and here, for a start. I'll make a fancy list of links for it real soon now.
I decided to write up the design documents for Final Battle Adventure: Online. Mainly so that the in-comic depiction is consistant and has a style - I'd rather get this all written out in advance than spend my time trying to work out the mechanics in the middle of the next FBAO arc.
So, to answer some of the questions:
Is it a real game?
No. Creating a 3D MMORPG requires a lot of time, expertise, and money. We don't have any of that. My goal is to design a game that, if it were real, would be believable and pretty cool. My goal is to make a game that people wonder if it's real or not.
Is this a parody of a game?
Sometimes. It's equal parts parody and the-game-I'd-want-to-play-if-it-existed, much like Hackmaster. There probably won't be too many deliberately broken parody bits, though.
Is it based on any one game?
No. It's influenced by a lot of things, though.
Is it the same in You Say it First and Namir Deiter?
No; the Hippedown server (YSIF) and the Sherup server (ND) don't have the exact same content. They have different rules. They're separate. Characters and items are not transferable from one to another. The Hippedown server lets characters have two classes instead of just one, for instance, and healing potions are rare. The out-of-character explanation is that Isabel is the sole writer for ND. I usually write the FBAO arcs in You Say it First, and we don't always have the same ideas about things. Also, we make most of this up as we go along.
Are there other servers?
Did we mention there being a Durri server? Yes, we did. Durri, mind you, is an island near Sherup. Cedric goes to art school there.
Is the FBAO site for the Hippedown or Sherup Server?
Both, officially. The information is more accurate for the Sherup Server, though.
Do the characters' races (fox, rabbit, etc) have any effect on the game? Not defined. Probably. It wouldn't be a proper fantasy RPG if it didn't.
Will FBAO show up in Spare Parts?