If you’ve watched Netflix’s “Emily in Paris” (or really any show that’s set in France), you’ve probably wondered how the actors have mastered their French accents—especially the ones who are faking it ...

A good Russian accent, such as the one Viggo Mortensen uses as Nikolai Luzhov in 2007’s “Eastern Promises,” brings an air of authenticity and drama to a performance. A bad one, however, like Arnold ...