So I see this occasionally where a character gets an outlandish reputation, and sometimes things as a result, without even meaning to. Some examples would be Kitano from Angel Densetsu, Blake from Yuusha ga Shinda! and Iruma from Mairimashita! Iruma-kun.

So I was thinking this could use its own term like Niwajin (made from Nise - fake, Uwasa - rumor and Jin - person)

So let's see some ideas and after we get enough suggestions let's do a vote on on it!!!

So to clarify (as I haven't read your examples yet), would this be where a character gets a larger than life reputation due to mishaps or being in the right place at the right time? Like how in One Piece, Buggy keeps getting credit for work other characters actually do?

Assuming I'm understanding, I like your term for niwajin so you have my vote.

Yes exactly that!!!