For anyone who's played through Mega Man Unlimited, you might remember that pesky little "boss fight" at the end of the game against a prototype of a particular character that appeared in future games (hey, doing my best to avoid spoilers here). Imagine if you could actually play as that character. Well now you can.
Mega Man Unlimited v1.3 introduces the Z-Prototype as a playable character...provide you've beaten the game on Original or Insta-Death mode AND save the game afterwards. Playing as Z-Prototype isn't canon to the story, can only be played in the main game, and instead of gaining new weapons like Mega Man, he obtains some new techniques in a fashion similar to Zero in Mega Man X4 (and possibly X5 and X6, but it's been too long since I've played those to remember).
Head on over to MegaPhilX's page to download v1.3 and take Z-Prototype for a spin...well, once you clear the game anyway.
