Wow, I am so envy of you. That's a rare experience for a Simmer and the game select you as the first for a candidate, rarespawn!
I haven't had a chance to try this. I really want to know if this things can be happened too to my Sims. Yeah, it's really weird but also fascinating in another perspective when you do look that way 
Besides the physical appearance. How about the data of your Sims hubby? It's also copied too? Like favorites, traits?
It seems to be just the appearance. Even the little portrait in the corner changes, and the head portrait when you are clicking on interaction options. Also on the friends tab, that portrait changes too.
I wasn't in control of the guy right away the first time it happened, only after we got married. I did check his traits though, because I was worried for my immortal dynasty and his traits were the same as indicated previously, only his appearance had changed. I was really worried that he wouldn't change back because I saved and logged out, and he still looked like my clone. I just figured I would play awhile to see if he could change back, like if he went to work or whatever. That was when I discovered he changed back after entering the shower!
I'll try to find the screenshot of it happening a second time. I don't have a before one, because like I said above, I wasn't really paying attention to them at the time. I only have the after shot of the two clones.
Edit: Here is the screenshot of the second instance.
