ExtrasDreamcast GD-ROM contains Bonus directory with five swimwear pin-up posters featuring the DOA girls. These are standard BMP images which you can read with your computer and use as desktop wallpaper for example.
Hidden introThe Dreamcast versions of the game include a hidden intro for Kasumi that shows her naked in a cloning vat. Additionally as this is an engine-based cutscene you can hack the console with a Game Shark and use the naked model in-game.
ReferencesOnce again, Ryu Hayabusa from Tecmo's Ninja Gaiden series makes an appearance. This time, one of his bonus costumes is the outfit he wore in the old NES game trilogy.
SexThis game shamelessly used as marketing a plug it's lineup of female fighters both before and after it's release with a series of..uhm..."suggestive" official swimsuit images released before the game, and the inclusion of, among other things, catwoman suits and schoolgirl uniforms as bonus outfits in the PS2 release.
Shadow ManThe European Dreamcast version has a Shadow Man costume for the character Zack, since it was released by Acclaim, the publisher and developer of Shadow Man.
Interestingly enough, all following versions of DOA2 (such as Hardcore or the upgraded version on DOA Ultimate) still feature Zack's Shadow Man costume, despite the fact that Acclaim wasn't involved in any of them.
Version differencesThe only real difference between this version and its others is the lighting effects. In the PS2 version, the lighting was very bright and made it kind of hard to see. In fact, there have been some reports of people having eye problems from the lighting.
There are six versions of Dead or Alive 2 so far: First came the original Dreamcast port which was pretty much a carbon-copy port of the original arcade release, then the PS2 port which added a few extras but had some graphical issues. The lighting was very bright and made it kind of hard to see. In fact, there have been some reports of people having eye problems from the lighting. An expanded Dreamcast port then followed which included all of the extras from the PS2 version which was then followed with the "Hardcore" release that fixed most of the graphic glitches and added tons of extra material. Finally, even more stuff (such as conceptual galleries and story events) was added for the Japanese "Hardcore" release.
The sixth and final version is the X-box remake Dead or Alive Ultimate, which uses Xtreme Beach Volleyball's engine and adds even more stuff as well as online play.
Information also contributed by karttu, M4R14N0, NightKid32 and Zovni