The phrase "bad penny" means someone or something that keeps coming back even though you don't want it to. It can refer to people who are unpleasant or troublesome and seem to always reappear in your life. Full definition
That's why bad penny stocks always outnumber good ones. (tsinetwork.ca)
In this area at least, it appears that the FCA have begun to weed the true bad pennies from the world of payday lending. (earthandmoney.ca)
And like that proverbial bad penny, Tokyopop is back with another Disney series, this one previously published by the black sheep of manga publishers. (manga.jadedragononline.com)