Kristen Stewart hurt herself "constantly" on "American Ultra" set

Kristen Stewart is known for her roles in dramatic films, like the "Twilight" series, "Still Alice" and "Into the Wild," but the actress is diving headfirst into comedy with the new movie "American Ultra."

The stoner-comedy-action movie features co-stars Stewart and Jesse Eisenberg; Stewart plays Phoebe, girlfriend to Eisenberg's Mike Howell, who works at a mini-mart. The couple are two stoners in West Virginia who suddenly find themselves fighting CIA operatives after Howell runs into a customer who says the words that remind Howell he used to be an assassin for the agency.

"This is hilarious," Stewart told CBS. "This is something light. I can hang out with Jesse for a couple of months and do something."

Stewart and Eisenberg use unexpected weapons in the movie, including spoons and mascara tubes, to great comic effect. The pair had months of special fight training for the movie.

"It looks realistic, it looks like these real people who are not action movie actors stuck in this situation," explained Eisenberg.

Stewart says comedy, especially action-comedy, is no breeze. "[It] ended up being the hardest job, emotionally, physically, like hurt myself constantly. All the scenes are like level 10 dramatic, cause the characters are reacting but that's what makes it really funny."

"American Ultra" opens in movie theaters Friday.