The knights-errant - strong emphasize on the errant - behind the adventure comedy "Your Highness" spend more time wallowing in medieval filth than weaving clever laughs and engaging action.

Reuniting key players from "Pineapple Express" - James Franco, Danny McBride, director David Gordon Green - "Your Highness" plays like a Middle Ages role-playing fantasy dreamed up by the giggly stoners of that earlier comedy.

Co-writer McBride and his collaborators apparently set out on a quest to ram as much coarse language and as many adolescent sexual gags into a movie as possible, maybe to cover the fact that the movie doesn't contain much else.

A healthy dose of modern frat-boy crudeness might have been refreshing in this story of two princes out to rescue a damsel from an evil wizard. Sort of "The Princess Bride" as retold in colorful sailor's vernacular.

Crassness overwhelms "Your Highness," though, the vulgar language losing all force by incessant repetition, deadening the lingo so that even the occasional witty wisecracks aren't funny.

This is McBride's show, explaining why he has top billing over Franco and co-stars Natalie Portman and Zooey Deschanel.
McBride, who shares screenplay credit with longtime writing partner Ben Best, plays slacker Prince Thadeous, defiler of dwarf queens, partaker of illicit apothecary herbs and all-around palace loser.

Older brother Fabious (Franco) is heir to the throne and the kingdom's golden boy, newly returned from a heroic quest with ravishing bride-to-be Belladonna (Deschanel) in tow.

After sorcerer Leezar (Justin Theroux) abducts Belladonna as part of his scheme to gain unstoppable powers, Thadeous must reluctantly accompany his brother to fetch her back.

On the road, they team with the mysterious Isabel (Portman), a lethal warrior with her own grudge against Leezar.
Despite the colorful costumes, mythological beasties and salty language, "Your Highness" is a tired tale whose few laughs fail to liven up the lumbering action.
Much of the supporting cast, among them Damian Lewis, Toby Jones and Rasmus Hardiker, barely register, even though they're integral to the action.

With even a little pep, any one of them could have upstaged the lead players, who are monotonous throughout. McBride sticks to boorish-oaf mode, Portman plays the stoic hero with blandness reminiscent of her "Star Wars" days, and Franco shows about as much verve as he did as co-host of the Academy Awards.

There's a delightful sense of bawdiness in Chaucer and other medieval literature, but vulgarity seems the main intent of "Your Highness." The movie chokes on its own dreary discourtesies.

Here's one of the milder ones: "You smell like the underside of a sheep's scrotum."

Oh, you knaves and jesters.