The FX crime drama “Justified,” which began its sixth and final season on Tuesday, unfolds in a fictional version of Harlan County, Ky. — a place of cellphones and late-model sedans that nonetheless “may as well be wherever ‘Harry Potter’ takes place,” said Jere Burns, whose conniving Wynn Duffy is a fan favorite. “I don’t know what that’s called, but it may as well be that, because you have people there who would not seem to exist anywhere else.”

Such eccentrics are key to the gonzo tone of “Justified,” which is based on stories by the crime laureate Elmore Leonard. Timothy Olyphant, as Raylan Givens, and Walton Goggins, as Boyd Crowder, represent the bourbon-soaked yin and yang of the series. But a galaxy of guest stars — whether fretting over stolen kidneys, living in R.V.s or stuffing bills into dead pigs — have over the years added both outré detail and a geographical constancy to what might otherwise be a more methodical, rural cops-and-robbers show.

Most began as bit players well aware of the fragility of life on a series with a high body count. David Meunier, who played Johnny Crowder, Boyd’s cousin-emy, said that a seemingly innocent inquiry — Have you read the next script? — became a frequent joke among the guest stars.

“The response was: ‘No I haven’t, do I die?! Am I dead?’ ” he said. “There was always that sort of hanging question.”