The theatrical love child of the 'Jackass' brand and hidden camera hijinks of 'Borat' is this barrage of chuckles.
'Bad Grandpa' is essentially a series of pranks loosely tied together by a narrative. It aims for big laughs, with increasingly brazen stunts, and attempts to tell a heartfelt story of an estranged grandfather and grandson bonding over fart jokes. But this 'Jackass' spin-off barely manages a steady stream of chuckle-worthy bits and a clunky, ill-executed story.
The first three 'Jackass' movies worked because they were exactly as advertised: jackasses stupidly pulling off jackass stunts. This simplicity allowed them to focus solely on crafting insane bits - which is why all three 'Jackass' movies are hilarious. But the story arc that is supposed to legitimize 'Bad Grandpa' feels more like an excuse for non sequitur gags.
'Borat' proves that a series of vaguely-related scenes can be assembled together into a coherent and hilarious story. 'Grandpa' strives to tell the story of lonely old man and a neglected child - but these surprisingly dramatic moments are often poorly-acted scenes that considerably slow the film down.
A weak 'Grandpa' story arc could have been forgiven or even overlooked if only the pranks were funnier. Most of the prank gags fall into one-of-two buckets: either 'dirty old man' jokes or 'kid says something shocking' gags. This eventually makes the jokes predictable
All that said, when this hidden camera comedy does nail huge laughs, it's because the filmmakers capitalize on the movie's biggest stars: the unsuspecting public. The horrified/shocked/dumbstruck reactions of onlookers are absolutely priceless. And in the end, disturbing the public is the true goal of the Irving Zisman character.
Final verdict: 'Bad Grandpa' isn't nearly as funny as it aims to be and its oddly dramatic moments are flat. While just about every stunt scene earns a good chuckle, the truly hilarious moments are too sparse to call 'Grandpa' hilarious overall.