Do you think we will ever find out how his skin came to look like a "crocodile?" Multiple episodes have shown him before becoming the dark one and then afterwards as well. Was this transformation simply from acquiring magic or what?
I was under the impression it's just the Dark One skin - Zoso had it, and Rumple got it, immediately after killing Zoso. I think the reason he doesn't have it in Storybrooke is because of the whole magic behaving differently in that world thing.
I thought it was a mark of corruption and how much he was in the grip of theDark One curse. Remember shortly after he got the curse and when Belle was at the castle the skin was not that bad but near the end the skin was more reptillian.