[KLHJ2]

Originally Posted by Trample the Elderly

He didn't play himself in the movie.

True, but it was his improvisation and dialogue. According to Wiki he wrote his own lines.

he was only intended to be the technical advisor, but Kubrick changed his mind after Ermey put together an instructional tape to convince Kubrick he was the right person for the role, in which Ermey went on an extended hair-raising drill instructor tirade towards several Royal Marines cast as extras, all the while being pelted by oranges and tennis balls, and managing to do so without repeating himself, stopping, or even flinching.[1] Kubrick allowed him to write his own dialogue and improvise on set (including a hilariously obscene observation on the proper etiquette of sodomy), a noted rarity

R. Lee Ermey - Wikipedia, the free encyclopedia