ParaNorman, the new stop-motion animated feature from LAIKA and Focus Features, presented an interesting challenge for its young actors, including Anna Kendrick, who voices the sister of the film’s protagonist.

Revolving around a group of kids trying to stop a zombie invasion of their town unleashed by a centuries-old curse, the film was Kendrick’s first time voice acting, and she admitted she couldn’t sit still, emoting as if she were on stage rather than in a sound booth.

“It’s kind of contained, so I always felt as though I was about to punch the wall,” she told a gathering of journalists in Los Angeles. “Casey Affleck was saying on our day together, which was both of our first days, ‘You need to get a camera on her knees, because she’s doing a lot of knee acting!’”

Kendrick made her acting debut at age 12, appearing on Broadway as Dinah in the musical High Society, for which she was nominated for a Tony Award. Since then she’s continuously acted in theater and film, although she told reporters she was especially thrilled to work on ParaNorman, as she learned that veteran actress Elaine Stritch would be playing Norman’s grandmother.

“That was a big thing, I didn’t know that until I got to my first recording day, and that was a really exciting piece of news,” she said. “I was like, ‘Tell me everything about her!’ and was sort of pumping them for information. I think she’s just such an incredible performer and tour de force human being that even though we don’t really get to work together, at least I get to be on the same IMDb page as her.”

Asked whether she knew was Stritch thought of turn in Camp, in which Kendrick sang “The Ladies Who Lunch,” the song Stritch immortalized on Broadway in 1970, the young actress said that in light of the veteran’s famous blunt honesty, “I don’t know and wouldn’t dare ask!”

“I’m fine not knowing!” Kendrick laughed.

Playing Courtney, the teenaged older sister of Norman (Kodi Smit-McPhee), Kendrick said she enjoyed voicing the self-absorbed cheerleader, describing her as, “The worst version of yourself at 16.”

“I liked the idea that I would be voicing all these mood swings, that she goes from being happy as a clam one second to acting as though it’s the end of the world because she spilled a bottle of nail polish,” she said. “I thought that would be a really fun thing to try to voice.”

Although she’s played somewhat similar characters in recent movies, such as her turn as the frustrated teenaged sister of the protagonist in Scott Pilgrim vs. The World, Kendrick thought the difference between ParaNorman’s Courtney and Scott Pilgrim’s Stacy boiled down to intention.

“With Stacy, she actually has Scott’s best interests at heart, and she’s right a lot of the time and has great advice,” she said, “and Courtney is just so selfish and awful and she just finds her brother really annoying. It’s not until the end that she kind of finds her supportive side. So I would say Stacy’s a much more mature version of the frustrated, annoyed sister.”

Kendrick also told reporters that unlike in other animated films, she actually participated in recording sessions with co-stars Smit-McPhee and Affleck, during which the directors encouraged them to improvise dialogue. They then re-recorded especially good or funny lines to use in the movie.

“I did find I harder to be mean to Kodi when he was in the room!” Kendrick said with a laugh.

She also drew inspiration from the Courtney puppet, telling reporters that Courtney’s crush on Mitch, Affleck’s character, made sense from a literally physical sense.

“One thing I like is that Courtney’s shaped like a triangle and Casey’s Mitch is an upside down triangle, so they fit together!” Kendrick joked.

Turning to her experience working with the film’s directors, Chris Butler (who also wrote the screenplay) and Sam Fell, Kendrick told reporters they sought her out for the role even though she had no voice-acting experience.

“I asked them if they offered it to me because of Twilight, because I play the obnoxious character in Twilight, and they said, ‘No, we just listened to you in interviews,’” Kendrick said. “One of the directors was saying they cut together one of my interviews with Casey’s interviews as if we were having a conversation to see what our voices sounded like, and I was asking if that was normal and one of them was like, ‘Yeah that’s pretty normal,’ and the other was like, ‘No, we’re crazy people!’”

Although Kendrick’s career has taken her from Broadway to the big screen, the actress said ParaNorman actually represented the type of project she loved the most – kid-adventure movies.

“I remember seeing Harry Potter and the Order of the Phoenix, and once it’s the kids on their own in the Department of Mysteries running through the halls, I had this moment where I realized this is one of my favorite kinds of movies: a bunch of kids on their own having an adventure where it doesn’t feel that any adults can come and help them,” Kendrick said. That’s a real treat for my inner child.”

As for what’s next for the versatile 26-year-old, Kendrick said she just finished an improvised movie in Chicago called Drinking Buddies, and will star in Pitch Perfect, a musical about an all-girl singing group, which opens Oct. 5.

“I’m like a singing, dancing machine! It’s a crazy movie about weird, weird girls and I like that,” she said. “I really understand the idea of trying to just be the best at something even if it’s really dorky and it’s not something you should brag about. It’s like King of Kong.”

“It’s not like these girls are going to be pop stars, they want to be the best at this really specific, really aggressively nerdy thing!” Kendrick added.

Although Courtney may be terrified of the zombies in ParaNorman, Kendrick concluded the interview by labeling herself an unbeliever when it comes to all things supernatural.

“I’m kind of a card-carrying skeptic,” she said. “I just got into an argument with Jake Johnson on [Drinking Buddies] where I was basically saying I don’t believe in ghosts and I think people who do are really silly -- and it came out later that he totally believes in ghosts and was like, ‘Oh, this girl’s mean!’”

ParaNorman opens Aug. 17.