"Wiseguy" can mean a made man in the mafia or a smart ass who acts like they are smarter than others. What I find interesting is that the Cantonese/Chinese slang term 古惑仔(Gu Wac Zai) has basically the same dual meaning. In this case, it's someone in the Chinese triad, or a mischievous/cunning person.
Pure coincidence? Or does anyone know if there's a connection between the two slangs in different languages?