Now... This is the Zenor Core which once was, with some obvious upgrades. I used to draw him like this, minus the fluffier chest and the left arm being very abnormal.
With this you can see more obviously that he isn't all that Hedgehog.
His arm does not have plate, it's part of the Chaos side of him which made his left shoulder, bicep and triceps into harder and sturdier material. Soft and cushy to the touch, hard and durable when you add pressure or impact hits it.

What triggers his change is a conflict with Leoh, no really. A lion named Leoh which is chief of the police back in his time. Yes, there will be a reference of him too.

Odds are, I can see a lot of people wishing I put him like this rather than the Sonic "knock-off" which I made him become.
The yellow arrows from each top spikes on each side go around his eyes, when he closes them, it is completely yellow rather than blue.