The Oscar winner stars alongside Robert Pattinson in `Water for Elephants` and the pair worked with several huge trunked creatures for the film.
The `Twilight` heartthrob has revealed the 35-year-old actress took an unexpected gust of flatulence from one of the large beasts when she was shooting a scene of circus tricks.
During an appearance on the `Jay Leno Show`, Robert said: "Reese ended up under the elephant, who then went back on its hind legs and let out the most incredible fart directly in Reese`s face for a good 45 seconds.
"It shows Reese`s complete commitment to do the job because she just stood there and took it. And the elephant`s got a big a**e!"
The 35-year-old actress wasn`t the only cast member to get up close and personal with one of the elephants.
Robert also revealed he climbed into one of the animal`s mouths during shooting
The 24-year-old actor said: "The first time I met Thai the elephant, I just got in her mouth. It just seemed like a good place to be!
"She had these huge lips and her teeth were all the way at the back so she just carried me around!"
The film stars Reese as circus performer Marlena Rosenbluth whose horse dies putting her act in jeopardy, until her husband - cruel animal trainer August Rosenbluth - buys her an elephant which leads her to find love with Robert`s vet character Jacob Jankowski.