i fast travelled to whiterun stables one day and then i walked around because i had to pickpocket some guy for a thieves guild quest, and i turn around and see 3 'louise letrush' NPC's walking around and when they talk each of their mouths kinda glitch out in the movement, but all make the same exact movement. here's a video of this strange and kinda cool occurance!!
http://www.youtube.com/watch?v=tNLxsnxqtVk
i thought it was pretty funny, but it's something bethesda should look into, because if there are cloning dragons and draugr death overlords or whatever it could be pretty unbalanced and frustrating.
theres also a few more videos messing around with these NPC's here!
http://www.youtube.com/user/TheMcartz33