Found a clone of an existing Sim

@nochopstix  Maybe the game liked your Sim so much it decided to make another one?  Just kidding but seriously I do not recall seeing this in my Sims 4 game. Did you talk to the "clone" long enough to see if they had the same traits? It would be interesting to find that Sim in Manage World and compare the two.  I am now curious to know what you discover.

Fun story and a joke on myself:  Sometimes I add my own households to the game for the household I am playing to meet and befriend. 

At least once I had mistakenly added the same household twice. Imagine my shock when I realized what I had done.
In any case unless there is some other weirdness going on I would say your find was a mere coincidence.

EQ Avid Sims Player
#EQCreations
I do not work for EA
All packs installed and patches are current.
PC / Win 10
Never used CC or mods.

@nochopstix I have seen this in my game and in my case it seems to have been a glitch that occurred when importing a household from my Library.

I had recently started a new game and I imported one of my Library Sims and her cat to be NPC neighbors of the Sim I was currently playing. Shortly afterwards I saw the NPC neighbor at a park, but then another Sim just like her showed up! I was like Huh? There are two of them?!? xD (Note to @EuphorialQueen : I am certain I did not import her twice). I checked them both with testingcheats + Modify in CAS, and one Sim had a cat in her household and the other did not, but other than that they appeared to be identical in all aspects. While I still had the doppelganger Sim opened in Modify in CAS I changed her name and appearance. Later on I found her in Manage Households and she was showing as a homeless townie. So she's still in that game but is no longer a creepy twin. xD

Btw- I was using CC in that game save & thought maybe that was somehow the cause of it? It's only ever happened that one time to me.