Memo to future comedy movie writers/directors: Setting a movie in medieval times but having the humor be modern is not funny. It didn’t work in “Year One” and it doesn’t work in David Gordon Green’s new film “Your Highness.”

I’m not sure why, it seems like it would work but for some reason stoner jokes coming out the mouth of a glorious knight in shining armor isn’t funny. It’s corny. Case in point, James Franco (who showed promise in Green’s earlier film “Pineapple Express”) as the honorable knight Fabious. It was agonizing listening to the Oscar nominee spout cheesy, heroic dialogue mixed in with sex jokes, gay jokes, and weed jokes. Not to mention his co-star, Oscar winner Natalie Portman as Isobel, a fierce warrior woman on a quest for revenge, who does pretty much the exact same thing.

The central character of the film is Thadeous (Danny McBride), Fabious’s younger, stupider brother. He’s lazy, a weed smoker (surprise!) and always gets into trouble. McBride (who was also in “Pineapple Express” as a wacky side character) just seems to play a wacky side character again in this movie, except with a British accent. Even though the movie was about him and his attempt to be heroic, he seemed to be there only as comic relief. Sure he was funny once or twice, but after about the fifth or sixth stoner joke or sexual joke, his act got old and eventually it felt like he was trying too hard.

After an evil wizard kidnaps his bride-to-be, Fabious, Thadeous and his girly assistant Courtney (Rasmus Hardiker) embark on a dangerous quest to go save her. Along the way they run into Isobel, who joins them.

But McBride’s lame performance is outdone by the unfunny and utterly predictable script written by McBride and Ben Best. Apparently they think that putting the f-word before every other word will somehow make it funny. And in addition to the stoner and sex jokes there were also some awkward ones thrown in, such as when a Minotaur tries to have sex with Courtney, thinking he’s a female. Or when Thadeous and Fabious go to a wise wizard, who turns out to be a pedophile. At times the film felt like a sketch comedy bit that goes on too long.

When the film is not trying to be funny, we are left with a boring quest movie, filled with dragon fights, wizard duels, and sword fights. In other words, one unbearable action scene after another and endless shots of the group walking across mountaintops while the camera zooms in overhead. The movie was only 102 minutes but man! it went by slow.

So if you want to make a comedy film, then fine but set it in modern times, and if you want to make a medieval movie, and maybe slide a few witty remarks in here or there, that’s fine too but don’t mix the two. The only medieval comedy to ever be funny was “Monty Python and the Holy Grail” and that’s because its humor was fresh and unexpected at that time. Whereas you can see the stale humor in “Your Highness” coming from a mile away.