Killer Instinct is (or was) property of Rare software. Though since Rare was purchased by Microsoft, where the developer slowly lost it's edge do to it's developers moving on (and lack of Nintendo's guidence). Microsoft has no interest in the series, I know that.
The original KI arcade game was a glorified advertisement for Nintendo's "Ultra 64" console. There was of course a brief teaser video about the "Ultra 64" that would run if the game was left idle. The Ultra 64 ultimately was renamed to the Nintendo 64. Though as I understand it the game did use the same basic hardware that would ultimately be in the Nintendo 64, there was one major difference. The game used an hard drive (I think it was 40MB). In fact I think it was the very first arcade game to use a hard disk instead of ROMs. This is how it was able to produce those cinema style scenes of players falling off buildings and such. It used pre-rendered video for these scenes.
KI wsa followed by KI2, which used the same hardware as the first game. KI2 was ultimately released as KI Gold for the N64, but all the pre-rendered scenes (which often we're shown when entering a stage) we're replaced with 3D effects to allow the game to fit on a 128 megabit cartridge. The effect worked but not quite as well as the arcade.
KI2 replaced two of the characters from KI with new ones, but there we're still just ten to choose from. KI2 also had a strange system where special moves would over power other special moves (like rock-paper-sissors). I didn't work very well though. And since the only real change to the game we're this addition no one really played it. At least in the arcade. They we're sick of KI by that point too (thank you Eyedol and your endless combo).
