This video (two parts) recently popped up on the official SC2 forums and a few other fansites. It shows a unique perspective of the Zerg including the 'Changeling' unit (near the end). This is what Cavez said about the Changeling earlier this year:
Overseers can create a Changeling by spending energy. The Changeling is a small unstable Zerg creature with timed life. When he gets near an enemy structure or unit he will change shape into the correct basic unit type and color to match that player. So if you get near a Blue Barracks you become a Blue Marine. If you get near a Red Stalker you become a Red Zealot, etc.
Enemy players cannot control the Changeling. It's still owned and controled by the Zerg player who created it. It is very vulnerable and can be killed by a single hit from just about anything. The Changeling cannot fight. He is just a shapeshifter, when he looks like a Marine that gun in his hand isn't "real."
You can see that something is a Changeling by mousing over the unit, by trying (and failing) to drag select or by selecting the unit and seeing the name and portrait.
What it does for the game: 1) Gives the Zerg a fun way to scout (though really they already have plenty of scouting options). 2) Makes enemy players constantly fearful of all of their own units. Is THAT a Changeling?! What about THAT GUY!?
In live games it is pretty difficult to keep on top of the "Changeling Problem" if an enemy Zerg player is trying to sneak into your base. However when you do catch them it feels pretty good.
It's something we have been trying for a few weeks and we thought we would include it in the WWI build to see what people thought.
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