Proteus' gravestone does not exist within Veronaville, so he can't be made playable without the use of hacks. As a result, the only indication of Proteus' existence is provided by the family tree of his descendants. According to his SimDNA in SimPE, his hair was brown before it turned grey. He is the only ancestor of his great great grandson Benedick, that also has dark blue eyes.
Proteus has no memories of his wife, and although he has the memory of doing WooHoo with Mystery Sim, he doesn't have the memory of Vincentio's birth. So basically apart from the WooHoo memory, he only has Create a Sim memories. Proteus has no skill points or personality points, and if he is resurrected with hacks, he will have a random set of interests.
Resurrection tip
This Sim has no character data and cannot be resurrected in-game. For more information, read this guide.