A person who looks like you, whom a mutual friend or acquaintance has photographed or tagged on social media. Or mentioned. Or put you in contact with. Whatever. You then confirm the verisimilitudinousness and end up being buddies. What could be easier, or freakier?
S: The pool attendant at my gym looks SOOOOOO much like you. I want to take his picture.
H: You should. I'd like to have him as my Face Buddy.