This question has probably been asked before, but anyway, in the spider colony with the fat spider bitch in the middle, you ask her how she became that way and she says that her former love "Jon Icarus" turned her that way, is this Jon Irenicus from BG2, did the Black Isle people change his name and forget about BG1 or did they just have a shortage of names?

They are indeed the same person.

Someone else can probably give more of the whys and wherefores, but as I've heard it, the designers of BG2 thought the name "Icarus" was too Greek for the Faerun universe, and changed his last name from "Icarus" to "Irenicus."

No wonder there was something familiar in Jon Irenicus when I started BG2.

A lot of names get used twice in the two games: "Sendai," "Hareishan," and "Brennan Risling" are three examples, and there's a reference to "Bodi" in BG1 to match up with "Bodhi" in BG2. The story is that while BG1 was being developed, several non-BioWare people helped int he design process by posting their ideas and opinions on a forum, and BioWare thanked them by incorporating their screen names into the actual game.

"Jon Icarus/Irenicus," however, is the only name that was meant to apply to the same character in both games. The continuity is a bit lacking, however: It's true that Icarus was his "working title" before they changed it to Irenicus, but in BG2 we learn that he almost certainly never had a wife, and the odds of him having an affair with a woman named Centeol and then turning her into a spider seem rather slim.

Ha ha I knew it was Jon Irenicus the fat lady meant.

Hmm ja turning someone into a spider seems like a weak punishment and too borring for Irenicus. Not enough blood and violence.