Of course everyone caught the Spiderman symbiote reference, but that isn't the only one with the Protectors!
From the Fantastic Four:
The Silver Surfer's power was from the board flowing silver metal over his skin, much like the Proteans flowing over our characters.
From Legend of Legaia:
The Proteans are like the seru who fuse with and corrupt people, and
the Protectors are like the Ra-Seru who assist people and try to help stop the Seru.
From Dragon Warrior series:
I'm sure i'm not the only one who noticed the Proteans look like Metal Slimes. Here's to hoping we'll fight a war with a variety of Protean hosts, and the boss is a giant one with a crown!
Some others noticed that the Protector set also just happens to be based on an older AK armor by nearly the same name. The Protector was said to be made of living metal, and has a little resemblance to the new one, though the eyes are red, the body is much more plain, and the spikes on the head are smaller.