The button on the back of his head makes his mouthplate move. The one on his shoulder is pushed backwards more like a lever (as opposed to downwards like a button) and makes the matrix light up when it's in his chest (swing open his chest panels and lift up the cover but don't look directly at it when you push the button. It's so bright, you'll go blind, trust me.
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I dont have Megs (so can't comment on it), but (Hasbro) Prime has alot more metal and feels more durable than Screamer. If you don't have either, and are only going for one, I would suggest the Prime mold. Unless Screamer is attatched to his flying stand, he is also less stable standing than Prime. And Prime has more poseability in his legs. Although mine does have a habit of dropping his legs off when I pick him up.
