For what it’s worth, "Bad Grandpa" – the latest set of idiotically inspired escapades from the "Jackass" boys – has one of the best fart jokes I’ve seen in quite a while. The titular raunchy granddad (Johnny Knoxville in pretty convincing old man makeup) and his lonely 8-year-old ward Billy (Jackson Nicoll) sit down at a diner and start having an innocent farting contest that, uh, escalates quickly and suddenly.

It’s a strong belly laugh that’s unfortunately surrounded by tepid little ones. I’d never be one to accuse the "Jackass" guys of doing something half-assed. After all, these are the same guys who launched themselves into the sky on a rocket, bloodily battled most of nature and did innumerable terrible things to the most delicate parts of their bodies (even in 3-D!), all in the name of gleefully juvenile entertainment.

But besides the previously mentioned Oscar nomination-caliber fart joke (they give out Oscars for fart jokes, right?), the stunts and sketches in "Bad Grandpa" never quite reach fever pitch.

In a first for "Jackass," there’s an actual story guiding the shenanigans this time around. When we first meet Irving Zisman (Knoxville), he’s meandering around his usual Nebraska haunts, getting his junk stuck in vending machines (let he who hasn’t gotten his man business stuck in a gas station Coke machine throw the first stone). After dislodging himself, the childishly lewd old man discovers out his wife has died. After a millisecond of sadness, Irving seizes his newfound widower status and vulgarly flirts with every woman who comes into eyeshot.  

His freedom, however, is short-lived. His drug addict daughter drops off his sweet, tubby grandson (Nicoll) on her way to prison for him to take care of. That simply will not do for Irving, so he packs up, throws the dead wife in the trunk (with the help of some amusingly shocked professional movers) and sets off on a road trip with Billy to drop him off at his deadbeat dad’s place in North Carolina.

Billy starts off as an annoyance, but he soon endears himself to ol’ Irving as an adorable wingman and fellow troublemaker. It’s almost kind of sweet, if you ignore the sagging old man parts, public intoxication and just general debauchery.

With the cross-country trip set-up, the easy comparison is Sacha Baron Cohen’s "Borat," minus the political commentary. "Bad Grandpa" has no interest in that; it’s just a candid camera tribute to bad behavior. He accidentally drops by a male strip club and ends up becoming a dancer himself, much to all of the patrons' horror. He catches a massive fish with strangely human set of male reproductive organs in front of baffled onlookers at a golf course and crashes a wedding with Billy in a very literal use of the word "crash."

The closest relative to "Bad Grandpa," though, is "Saturday Night Live," and not particularly in a good way. Each sketch starts out with a funny premise and has some amusing warm up jokes and reaction shots. When it comes time for the skits to really come through on the raucous laughter, it never seems to really deliver. The stunts just quickly peter out or, in the case of a late meeting between Irving and Billy’s dad in a bar filled with grizzled anti-child abuse bikers, the joke never comes at all.

The "Jackass" crew’s past theatrical efforts were brilliant in their slapdash simplicity: present the set-up, build the comedic tension and then hit with the big punch line with maybe a little bonus twist if they were feeling especially devious. Here, it requires a little bit more finesse (if such a word could be used in describing a movie involving fish gonads) that the film doesn’t quite have. Series director Jeff Tremaine seems to be fading out on scenes when they should be reaching their hilarious climaxes – my beloved fart sequences not included, of course.

There are still jokes to be enjoyed, especially from young Nicoll. More often than not, he ends up stealing the show right from underneath Knoxville with his humorous deadpan interactions with strangers, making them uncomfortable with candid talk of his drugged-out mom and persistently asking them to adopt him. And Knoxville is fully committed to pestering their hidden camera victims with his horny, ornery old man routine.

"Bad Grandpa" still entertains, but the amused, incredulous chuckles are more common than the massive big laughs you want from a movie like this. When a movie is dedicated to bad taste, you want to laugh hard and maybe feel bad about it afterward. In "Bad Grandpa," the guilty, "I should know better than this" laughs feel like exactly that, especially near the end when we show up at a children’s beauty pageant. It feels like going after low-hanging fruit, and strangely enough, I expect more creative, witty spark from my wild man children.

Maybe having a story and playing around exclusively in the real world wasn't the best tactic for the "Jackass" guys. When it was just the pranksters, galavanting in their isolated pain playgrounds and aiming their hijinks mostly at themselves, they felt free to do anything and everything. Here, they seem a bit timid (once again, as timid as you can get with public displays of dangling genitals) to go all out and let loose. The audience shares the feeling.

We'll always have that fart joke, though.