The last entry, dealing with recognizing people by their faces reminded me of the English expression "What's his face" used to refer to someone whose name you have forgotten. This in turn reminded me of a Japanese word I've seen but haven't quite payed attention to... yet.
Meaning: a certain somebody (usually it's obvious who is being referred to)
Literally: Mr. Someone, Mr. Somebody
I thought that this word might mean "What's his face" but it turns out that it doesn't. When you use "What's his face" you know who you have in mind but can't relate the information across to anyone else because you don't remember that person's name. Then usually you start a describing game until someone goes "Brad Pitt" and you go "YEEESSSS! THANK you!"
It turns out that with 誰かさん, the identity of the person is known to everyone and it's just a playful or cynical way to refer to that person. This is actually translated to English as the simple "someone/somebody" but has that special nuance that comes across in those types of sentences:
<looking at your chocolate covered kid's face>
"SOMEONE has been eating my chocolate..."
<and off to a COMPLETELY different scenario>
"SOMEBODY has been a bad girl... come over here!"
<on the more cynical side>
"Well, if a certain SOMEONE would have listened to me, we wouldn't have been stuck in the middle of the woods after sundown, now, would we?"
As for a Japanese word/expression meaning "What's his face", I didn't find one. If you know something that could be considered a translation for that, please let me know!