Mr. Ball, the Oscar-winning screenwriter of “American Beauty” and Emmy-winning creator of “Six Feet Under,” said that when he learned Ms. Paquin was interested in “True Blood,” his reaction was: “Really? That doesn’t — huh. She wants to do this?” He added: “At the time Anna was dark haired, and certainly her body of work didn’t lead me anywhere near Sookie Stackhouse.”

Ms. Paquin, whose eclectic résumé also includes “Almost Famous,” “She’s All That” and three “X-Men” movies, said she expected to be told: “She’s just not blonde enough as a person. Which, by the way, apparently is a thing, which I have heard before.” But with some tenacity, a few auditions and the help of a celebrity colorist, the role was soon hers.

“True Blood” had its premiere on HBO in 2008, when the network had recently lost signature shows like “The Sopranos” and “The Wire,” and in its first season went from about 1.4 million viewers for its debut to almost 2.5 million for its season finale; it now draws about 5 million viewers for new episodes.

Those numbers — stronger than those drawn by a critical darling like “Mad Men,” not so huge as phenomena like “The Walking Dead” or “Jersey Shore” — point to “True Blood” as a show that has built its audience through positive word of mouth and, perhaps, the curiosity stoked by a provocative Rolling Stone magazine cover. It has taken a little longer for its critical reputation to catch up. “True Blood” received its first Emmy nomination for outstanding drama only last year.

Over its first two seasons Sookie vied with a serial killer and an orgy-inspiring maenad; she was romanced by Bill and eyed lasciviously by a rival vampire, Eric (played by Alexander Skarsgard); she screamed a lot and got naked without much hesitation. “It certainly would be a bit of a buzz kill,” Ms. Paquin said, “if Sookie never took her clothes off, considering how often she has sex on the show.”

Mr. Ball said Ms. Paquin’s commitment to what could seem a ghoulish affair was essential to his vision, that it not be bodice-ripping “lady porn,” as romance novels are sometimes unfairly branded, but “about the terrors of intimacy.” And, he said, “it certainly helped that she and Stephen were falling in love in real life over the course of the first season, in helping sell that romance because it was so genuine.”