John Doe; Mr. Nobody
Colloquial and humorous term for an anonymous or unimportant person, often used when the speaker doesn't know or doesn't want to reveal someone's name.
The culprit was reported as John Doe.
誰がやったか知らないけど、名無しの権兵衛ってことでいいんじゃない？
I don't know who did it, but we can just call him Mr. Nobody, right?