For those who've been keeping tabs on Cameron Diaz's very R-rated upcoming comedy "Bad Teacher" — particularly the film's naughty red-band trailer — this is not the sweet and wholesome Diaz we've come to know and love via "There's Something About Mary" and "Charlie's Angels."

In "Bad Teacher," Diaz plays disgruntled educator Elizabeth, who, when not smoking "medicinal" marijuana in the parking lot, passing off the advances of the school's gym teacher (Jason Segel) and grading papers ("Are you f***ing kidding me?" she writes on one student's exam), keeps herself busy by seducing the new substitute teacher Scott (Justin Timberlake).

When MTV News caught up with Diaz recently, we asked her to talk about her character's "problems," and it turns out that the film's title is perfectly appropriate in this case.

"She's not a good teacher," Diaz said. "She is the opposite of good. She is a bad teacher. She is bad at teaching. ... She just really doesn't care. She doesn't want to be a good teacher, and so therefore, being a bad teacher really doesn't mean anything to her either."

Diaz said her character's professional ineptitude stems from a place of total misery.

"She's miserable. She's not happy with her world, and she doesn't pretend that she is," Diaz explained. "Her pain is real. She's living a very painful existence, so there's no humor to her in this."

With regard to the research the actress put into the role, Diaz revealed she took a few things from a bad teacher she once had.

"I had a really, really bad teacher. I'm not naming names. That teacher knows who that teacher is, and that's about it," she said. "I think that this person actually cared about being a good teacher, but just happened to be terrible," she added with a laugh. "We've all had those teachers. Teaching is not everybody's calling."

It's Summer Movie Preview Week, and MTV News will be bringing you exclusive interviews, clips and photos for the most anticipated films of the coming months. Get ready to gorge on inside looks at "Captain America," "The Hangover Part II," "X-Men: First Class," "Cowboys & Aliens" and more.

Check out everything we've got on "Bad Teacher."

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