AceShowbiz - Dakota Fanning nearly fainted during her first fitting for TV period drama The Alienist.

The War of the Worlds star plays the New York Police Department's first female cop on the show, which debuted earlier this year, and she has to look like an 1896 go-getter opposite a leading criminal psychologist, portrayed by Daniel Bruhl, and a newspaper illustrator (Luke Evans).

The costumes helped her get into character as a proper miss, but she admits squeezing into her first corset was not fun.

"One of the most important things about The Alienist was the costumes," she says. "I fainted during my first fitting. I had just gotten off the plane and was swollen and jet-lagged. They put the corset on, and I said, 'I'm going down!' I had to sit. But I got used to it."

"My body completely changed (while filming)," she adds. "For better or worse, the corset puts you into the character. It affects everything you do: breathing, walking, sitting, standing, and definitely eating."

And despite her discomfort, Dakota was thrilled that she really felt like she was living in the 19th century on the set of the dark TV drama.

"(Costume designer Michael Kaplan is) so incredible and so talented and very detail-oriented," she said in January. "I always say when you're filming things, if there's 50 buttons on a shirt, they (costume officials) might make them snaps to make it easier to get them on and off; not Michael!

"Fifty real buttons that are from the 1800s! Everything was very real, which was a privilege to wear, and I think that you can tell when you watch the episodes, the amount of detail on the sets, on the costumes, and the props - everything was authentic."