Like the Jackass movies, Bad Grandpa combines hidden camera filmmaking with scripted set-ups steeped in outrageous, often rudely sexual behavior. The humor, therefore, relies on the reactions of the unwitting onlookers, and our appreciation for dick jokes and fart jokes that evolve into something far more shocking.
Irving Zisman (Johnny Knoxville, layered in convincing makeup to look like an old man) is left to care for his 8-year-old grandson Billy by the kid's drug-addict mom. This doesn't fit into Zisman's plan, who is ready to party after the death of his wife. So he takes the boy on a cross-country road trip to North Carolina, where Billy's lowlife father is willing to take in his son because of the money he'll get through child support. Thus begins a journey where Irving gets to show just how bad of a grandpa he can be before arriving at their destination.
The idea of parental — or in this case, grandparental — neglect isn’t usually the stuff of comedy. Which makes this ripe material— or it should, but one of the problems with Bad Grandpa is how surprisingly tame it is. A few vignettes will elicit bursts of laughter, but too many fall flat before we're shuffled off to the next scene.
Because the audience is in on the joke that this is all a put-on, the mix of scripted drama and setups doesn’t quite gel. When Billy and Irving are alone, staying in character, we just want to go back to the pranks. Within the context of the story, the scenes are necessary. They're just not written that well.
While Irving is off on his own, he's embarrassing himself — usually in front of one or more women. The most oft-repeated joke — to the point of being tiresome — is Irving as lecherous old man, leering at women and talking about his desire to score some "poontang" and "tail." Meanwhile, Billy (Jackson Nicoll), who looks like the kind of kid who would hang out with Little Rascals, is coaxing unwitting pedestrians into engaging him and hearing embarrassing stories about his mom. The pudgy, shameless Nicoll is game for these antics, and he's an excellent actor, but even as he's calling strange men his new daddy, the laughs are hard to come by.
As a movie, Bad Grandpa isn't all that good. Only during the credits, do we see outtakes that capture the freewheeling, giddy humor we wish the film itself would have had throughout. Though not all of the jokes work, the few that do are pretty uproarious in their lewd, crude way. And for those attracted to a movie with the Jackass pedigree, that may be enough.