Sometimes being a movie critic is simply acting as a reporter and informing the reader what experience the movie in question has to offer. With comedies like Austin Powers, Napoleon Dynamite, and, yes, Jackass Presents: Bad Grandpa, I wouldn’t be doing my job without admitting right away that the audience and I laughed a great deal. In fact, I took my friend Tom with me and, while he’s a jovial, good-humored guy, I’ve never seen him laugh so hard in my life. It’s important that this gets mentioned early in the review, as it may be a key factor in whether you, the reader, decide to spend your money on a movie this dumb.

Jackass master of ceremonies Johnny Knoxville dons convincing old age make-up, drives around the country with a young boy and fools multitudes of people into thinking they’re witnessing an elderly man behaving horribly with his grandson. On the one hand, this is a Candid Camera sort of movie, in which the laughs come from seeing real people react to Knoxville’s elaborate prank. This was where the movie had me on board, with the unplanned reactions and ability of Knoxville and this kid (Jackson Nicoll, a real find and a gifted improviser) to pull off the most outrageous scenarios with fiendish panache.

The problem is, we’re also supposed to take the “plot” semi-seriously and believe we’re watching a real movie. We get a loose and familiar story, in which the randy grandpa will bond with his grandson on a long road trip to the boy’s neglectful father. To say the least, this is the stuff of the most generic, uninspired kind of formula comedy, and it’s mixed in with all the good stuff.

Perhaps we’re supposed to overlook the story and just soak up the laughs but the movie wants to have it both ways and it often stops the movie cold. We’re in on the joke, of course, and know that Knoxville and the kid are doing routines on people that may have unexpected outcomes, as the biggest laughs come from just how far people on the street are willing to buy into Knoxville’s bits. These scenes work.

Then we’re taken back into the plot, which is thin and uninspired. Couldn’t they have just dropped the lame “story” and just given us one funny bit after another? After all, isn’t that the format of the Jackass movies and TV series? Why did Knoxville think we needed another tired redux of Big Daddy?

Knoxville’s geriatric make-up does most of the acting for him, as he barely modifies his old man voice from his actual vocals. This is hardly performance art, let alone a great comic performance. More like that college prankster who pulls a fast one on his best friend and drunkenly laughs about it for days later. I want to give him the credit he deserves, as he knows what’s funny and gives his all to the project but this isn’t on the same level of brilliant improvisation and insane commitment to character as Sacha Baron Cohen’s Borat.

Without giving away the punch lines, I’ll single out a scene in a diner involving a fart contest between grandfather and grandson. There’s also a beauty pageant that gets gloriously hijacked and a funeral that goes from bad to hilariously unbearable. These scenes are gross, in poor taste, and rely on the lowest of low brow humor.

More importantly, they’re awfully funny. Too bad we’re saddled with a needless plot that weighs the movie down. Once it’s on DVD, I’ll skip past the stupidly sentimental story and go straight to the good stuff.

Jackass Presents: Bad Grandpa
★ ★
Rated R / 92 Min.