Your Highness is a double-negative; whatever there is about the film that might be good or worthwhile is cancelled out by all the parts that aren't really worth the time and trouble. I'm sure everyone must have had a great time making the film, but that's hardly a reason to spend millions of dollars to make the thing. Ostensibly, it's about entertaining the audience with some vulgar, somewhat-lowbrow comedy. And, at that, it mainly fails.
Somehow a pretty good cast got roped into this. Danny McBride had worked quite a bit with the director, David Gordon Green, during Pineapple Express and "Eastbound & Down"; James Franco starred in Pineapple Express, so obviously there was already a bond there. For the life of me, I don't know what Natalie Portman and Zooey Deschanel are doing in this, much less Toby Jones and Damien Lewis. It's a very odd mix of actors that I wouldn't have quite imagined for a comedy like this. They all do an admirable job, though some are a bit underused. In fact, most of the movie feels like there should be more going on. And what's there should be funnier.
The script was written by McBride and Ben Best, McBride's co-writer on The Foot Fist Way and co-creator of "Eastboound & Down". They do what they always do and much of it was as-advertised: a fantasy movie filled with cursing and vulgar content. Unfortunately, aside from McBride's usual brash awkwardness, bravado, and irritably foul mouth, much of the movie's attempt at comedy is stagnant. The combination of silly vulgarity and scenes of awkward pauses don't quite mesh. What hilarity there is much too little and too far between.
The one area that the movie excels at is the fantasy atmosphere and effects. It pulls off the fantasy film better than most serious fantasy movies; as a comedy and ostensible parody, it really shouldn't be a head above most fantasy fare. And, yet, it does a better job with action, monsters, and effects than movies with higher budgets. That shows a real love for the source material and makes me wish that there was a bit more to the movie to make it more exciting. But a severed penis and some cursing can't quite make that 100 minutes into more than 45 minutes worth of content.
There was easily more room to play with the genre, more jokes to be had, more to be done with the actors and their characters, and generally more entertainment to be mined out of the concept, but the movie just missed it, settling for cute or occassionally amusing when it could have fought harder to be truly funny. A missed opportunity if I've ever seen one.