1104_pattinson_singleReal-life couple Kristen Stewart and Robert Pattinson got a little too passionate during their "Breaking Dawn" sex scene -- almost earning the "Twilight" film an "R" rating!

"[There are MPAA] guidelines on thrusting intercourse," director Bill Condon tells Celebuzz. "[Kristin] got very into it." Um ... TMI!

Condon says the original scene was not quite at the desired PG-13 level -- so it was re-cut to make it more appropriate.

"[The scene] was so much more about romance than it was about hot-and-heavy action," Condon tells MTV. "So it was a very kind of simple adjustment to make."

Kristen herself agreed that she may have gotten carried away -- calling the whole bedroom shoot "surreal."

"It was so weird, it didn't even feel like we were doing a 'Twilight' film," she tells Access Hollywood. "I was like, 'Bella! What are you doing? Wow! What is happening here?'"

"The Twilight Saga: Breaking Dawn Part I" is in theaters Nov. 18.