This game was released in North America (as Monster party), but there was different version planned for Japan that went unreleased. Years ago, a Japanese collector purchased a prototype of this game for an obscene amount of money, and went out of his way to say that he was not going to share anything about this game (screenshots, videos, ROM image). A second copy of the prototype was found, and it looks like someone has dumped it. Mike from Nintendo Player has written a short article about it. Looks like someone was trying to stir things up by leaking it out.
http://www.nintendoplayer.com/news/u...investigation/