One character’s diarrhea under duress is a running joke in Miss March, so perhaps it’s appropriate that this fitfully funny comedy winds up crapping the bed in the end.

At best, this lewder, cruder spin on last year’s Sex Drive has a disarmingly daffy shaggy-dog touch a la Half Baked or The Brothers Solomon. More often, it’s like a Dane Cook “romantic” comedy or the eminently execrable Tomcats.

Trevor Moore and Zach Cregger — two-fifths of the comedy troupe The Whitest Kids U’Know — write, direct and star in Miss March. The troupe would’ve bounded through a similar story in truncated fashion — and likely with more absurd laughs — on their IFC sketch show. Instead, situational or sight-gag punchlines are deflated by dialogue that calls attention to them.

Surreal touches of the series occasionally sneak into a story slender even by sex-comedy standards. (Best are the psychotic firemen, physically impossible rap-song choruses and characters ordering tater tots and Jäger shots at a fine restaurant.)

Cregger plays Eugene, a straight-arrow high-school student who actively promotes celibacy, along with his girlfriend, Cindi (Raquel Alessi).

Eugene is happy to wait until marriage to make it with Cindi, but Cindi — knowing Eugene is the one — wants to make prom night magical. Somewhat reluctantly, he agrees to lose his virginity.

All well and good until Eugene gets schnockered on whiskey — provided as a social lubricant by his boorish best friend Tucker (Moore). After stumbling down a flight of stairs, Eugene goes into a coma.

Four years later, he awakens to learn that Cindi is now a Playboy model, and, with Tucker in tow, seeks out his sweetheart at the Playboy Mansion. Also on the journey is a rapping friend of the pair (Craig Robinson), with a name and hit single that are unprintable in this forum. (Just remember the “.MPEG” designation on his name.)

Cregger makes a sufficient straight man; his pinched-up face makes a scene where he pumps gas after years of muscular atrophy funnier than it should be. The problem is that the script puts Eugene perilously close to being a virginally ideological jerk.

Worse yet is Moore’s performance, from which any of his raffish TV-screen charm has been evaporated. Here, he comes across as a desperately loud mix of Jim Carrey, Brendan Fraser and Tom Green. As more and more women walk away from him at the Mansion, viewers will want to do the same.

There are nuggets of puerile parody that work — namely how quickly the obsession with female nudity begins and how long it lasts. But by the time one woman picks a lock by fellating it, and another enjoys champagne spiked with dog urine, Miss March is all turn-offs.

Miss March does little to buck the idea that comedies often aren’t worth the extra cash of a Blu-ray purchase. Though on a BD-50-sized disc, its 1080p AVC MPEG-4 transfer frequently looks no better than an upconverted DVD. Also, what actually are PowerPoint-esque slide-ins of the opening titles look like pixilation at first.

The DTS-HD Master Audio 5.1 lossless track also doesn’t amount to much, save some purposefully clanging Foley effects and the amusingly overwrought bass whenever Robinson’s character is rapping.

The Blu-ray offers the choice of the theatrical cut (89 minutes) or the unrated cut (90 minutes). Never having seen the former, it’s a guess that the latter adds the status-quo extra nipple or two. (It’s a hope that the extra goodies aren’t the horrifying shot of one character’s disfigured genitalia.)

Extras include a brief featurette on Robinson’s rap star, as well as a series of viral videos; Sound Design, in which Cregger and Moore show how they made the film’s sound effects; and a series of auditions that feature Cregger and Moore’s sadly missing co-stars from The Whitest Kids U’Know.