Although the film was written by Ben Best and Danny McBride, the dialogue is heavily improvised. Director David Gordon Green said there was never a script used on-set. Only the plot outline and written notes were used.
The premise for the movie evolved from a frivolous game David Gordon Green and Danny McBride used to play to while away on film sets. Each would take turns in suggesting a title for a film, and the other would try to concoct a viable storyline. When the title "Your Highness" was put forward, the premise was, "It's about a Prince who gets stoned and fights dragons."
During filming, James Franco flew back and forth between New York City and Belfast, because he was attending full-time classes in college.
Natalie Portman admitted she only did this movie because there was some uncertainty if Cisne Negro (2010) would get green-lit by a major studio. She signed on to this film for a paycheck, and use it to help finance Black Swan herself, should the need have ever risen. However, Black Swan got green-lit, and went underway fairly easily, and Natalie got stuck doing this film having already signed on.