Edward and Bella Cullen in bed as Bella loses her virginity.

Robert Pattinson finds it hard to keep a secret. Although he’s currently promoting his new movie “Water for Elephants,” he also spilled a few beans about key scenes with Kristen Stewart in “Break Dawn,” the last film in the Twilight series.

Pattinson met with USAToday reporter Andrea Mandell in Vancouver and called “Breaking Dawn,” which is being filmed in two parts, “outside the box” compared with Twilight Films, “New Moon” and “Eclipse.”

Each sequel has grown more action oriented and darker compared with the original “Twilight,” which was largely devoted to explaining the characters and scene setting.

Check out Rob’s Water for Elephants photos.
Click to enlarge.

Now it seems, Breaking Dawn may be the darkest and far racier than the other films. “It’s really different from the other ones,” Pattinson said.

“There are some days on set just watching you go ‘How is this going to be PG-13?’ It’s like totally ridiculous,” he added.

Among other things, the movie will include a birth scene when Kristen’s character Bella Swan has a half-human, half-vampire child.

Rob called the filming the scene “kind of hilarious.”

“She has to have this pregnant suit on all the time, that was probably more annoying for her,” he said.

Until know, Bella has been introverted and awkward. The only thing she is adamant about is her love for Edward. But once she becomes a vampire, look out!

“I can’t give too much away but there’s some bits, especially towards the end of the movie, she’s just like the polar opposite of any of the other (films),” Rob said.

“I mean, she’s a different person, which is cool. She looks completely different. She looks probably the most convincing vampire out of all of us.”

“She suits being a vampire.”

The wedding scene will be one of the highlights of “Breaking Dawn” and is still to be shot.

“That’s a hard scene too,” Rob told the newspaper.

Rob will next appear on the big screen (April 22) in “Water for Elephants,” with Reese Witherspoon and Christolph Waltz.

That film apparently had its moments, too.

“I had to get knocked down by a horse. That was terrifying,” Pattinson recounts.

“It was just one split second but [it was] a fully grown stallion. I’m kind of relatively scared of horses as well. I’m just glad I didn’t have to ride any of them. I’m not particularly good at horse riding.”

Indeed, most of the riding was left up to Reese; check out the newly released behind-the-scenes outtakes from the movie.

It looks like it will be a pretty sweeping production.