If you've seen any of the Jackass movies then you've seen Johnny Knoxville made up to look like an old man. He's very convincing, thanks to the great make-up and his attitude. There were a number of sketches filmed in which Knoxville played, funnily enough, a bad grandpa. He would sit down somewhere with a young kid and allow them to drink alcohol. When taken to task, he would always make the situation worse by being downright unrepentant and clearly spoiling for a fight.
Bad Grandpa is, as you might already suspect, more of the same. It's a road movie that crafts a loosely-plotted storyline around some semi-improvisational skits, taking in a good number of innocent bystanders in the process. Knoxville is Irving Zisman, the man suddenly landed with a grandson named Billy (Jackson Nicoll). He aims to deliver Billy to his father (Greg Harris), despite the fact that the man sees his son as nothing more than a way to get his hands on an extra $600 a month. And that's all the plot that you need to create a film full of amusing stunts that range from a disastrous funeral to an altercation with some male strippers, and more besides.
If you're after something subtle and sophisticated then you're looking in the wrong place. To be fair, this was marketed as "Jackass Presents: Bad Grandpa" as opposed to just "Bad Grandpa". I know this was mainly done for marketing purposes, but it also serves as a warning to those who dislike Knoxville and co.
The two stars do a surprisingly great job of making their characters feel very real. This could have easily been a simple selection of broad skits with no need to work on any of the linking material, but that's not the case. Knoxville and Nicoll work brilliantly alongside one another, and the biggest surprise is how genuine the fragile bond between them feels. Harris is pretty funny as the deadbeat dad who doesn't want his son with him until he's made aware of the money he could receive, and his bravery is to be commended for his behaviour in the third act (you'll have to watch it to know what I mean).
It seems redundant to mention the direction from Jeff Tremaine. Yes, the movie is put together competently. Even the footage filmed via hidden cameras is decent, with a variety of tricks used to keep the whole thing feeling more like a movie than just a set of sketches. Yet, at the end of the day, it IS little more than just a set of sketches. They're good, and one or two may make you laugh aloud, but the joke isn't enough to sustain a feature.
Watch and enjoy. You may well laugh a lot more than I did. I just doubt that this is one to revisit again and again, unlike some of the previous Jackass presentations.