The fortieth time you hear the F-bomb in a Medieval setting isn’t nearly as funny as the fourth or fifth. That’s the shortcoming of the central conceit of “Your Highness,” a raunchy stoner comedy in  tights from Team “Pineapple Express.”

A Danny McBride vehicle directed and photographed by his pals from film school (University of North Carolina School of the Arts), it’s a sporadically funny farce that plops McBride, James Franco, Natalie Portman and Zooey Deschanel in a world of dungeons and dragons, bongs and BJ jokes.

Franco plays the dashing, quest-happy heir to the throne of the Kingdom of Mourn. McBride is his cowardly, resentful and potty-mouthed younger brother. When Fabious (Franco) returns from a quest with a fiance, Bella Donna (a dopey version of Deschanel). Thadeous (McBride) can’t even be bothered to show up at the nuptials. And he’s best man.

But that wedding is where Bella Donna is kidnapped by the evil wizard Leezar (Justin Theroux). Thus, Fabious has his quest. And this time, Dad (Charles Dance) insists Thadeous tag along.

There is a pervert wizard (puppet) to visit, a labyrinth to be navigated and a minotaur whose sexual advances are to be resisted. And let’s not forget the topless Amazons ruled by a baby-faced brute who unleashes a dragon on them. An archer on her own quest (Natalie Portman) soon joins their not very merry band.

It’s meant to be faintly Pythonesque with a hint of  bowdlerized “The Black Adder.”

“You smell like the underside of a sheep’s scrotum.”

But it’s entirely too slow of foot for that comparison to pay off. McBride falls short as a comic leading man even as he stays in character — arch and arrogant and sniveling, with his bursts of “Hangover” level profanity serving as too many of his punchlines.

“Your vulgarity masks your pain.”

David Gordon Green’s (“Pineapple Express”) action beats are perfectly serviceable — a stagecoach chase, assorted sword fights, a duel with a five headed dragon that is a bloodier version of what we saw in “How to Train your Dragon.” The effects are generic and just a tad cheesy (lightning bolts from the fingers, etc.).

Naturally there’s a hookah, a chastity-belt thong and the comic jolt of Oscar winner Portman talking tougher and dirtier than even the boys. At least Franco looks more at home here than he did on Oscar night.

There are enough laughs to get by and one can excuse the dead stretches (20 minutes too long?) and the tedious gay jokes and the ways the story violates basic “Become a man, wimpy brother” and fantasy quest conventions.  What’s less forgivable is the cynicism, the sense that a lot of people wanting to cash in on another lowbrow hit went out to get’em one.

MPAA rating: R for strong crude and sexual content, pervasive language, nudity, violence and some drug use.

Cast:. Danny McBride, James Franco, Natalie Portman, Justin Theroux, Zooey Deschanel, Charles Dance

Credits: Directed by David Gordon Green, written by Danny McBride and Ben Best. A  Universal release. Running time: 1:42.