Long before Ben Carson ran for president he starred in the Farrelly brothers movie 'Stuck on You'

Retired neurosurgeon Ben Carson is currently trying to build a campaign that can get him the Republican nomination for the 2016 presidential election. But there's one thing that sets him apart from his other opponents - he has starred in a Farrelly brothers comedy.

Carson has a cameo in the brothers' 2003 movie "Stuck on You," starring Matt Damon and Greg Kenner as conjoined twins.

In the scene, Carson plays the doctor who attempts to separate them. He even had some lines opposite Eva Mendes.

Following the operation he goes into the waiting room and tells the conjoined twins' girlfriends, one of them played by Mendes, the outcome.

"Look, I don't quite know how to tell you guys this," Carson said, "But we lost them."

The girls are in shock until another doctor rushes in and tells Carson's character, "Good news, we found Bob and Walt. Someone took them upstairs."

Carson acts relieved and tells the girls, "By the way, the operation was a smashing success." Followed by a shove from Mendes' character.

Carson told The Baltimore Sun back in 2003 regarding the role, "If it was going to be raunchy or offensive, or degrading or demeaning to anybody, I wasn't going to do it."

According to the story in The Sun, Carson declined to be paid for the role and instead got the producers to agree to premiere the film in Baltimore with proceeds of the event going to two of his charities.

The casting of Carson as the doctor makes sense. In 1987, he became the first surgeon to successfully separate conjoined twins at the head.

Watch Carson's waiting room scene in "Stuck on You."