1. Dirty Grandpa is even worse than you think it is, and I bet you think it’s pretty bad. There’s no reason, inherently, that a movie called Dirty Grandpa, even one starring one of the greatest actors of our time, has to be bad. The idea that a comedy is supposed to have taste, that certain jokes should be beneath us, is wrong-headed and dismissive; all that is required of a joke is that it be funny. There is a way, in a theoretical universe, that a scene where Robert DeNiro masturbates on his couch while watching amateur porn involving elderly people could be funny. I don’t know where this theoretical universe is, and I suspect I wouldn’t want to live there, but it could exist. It requires set up, and dedication to the joke, and a cheerful willingness to take every comedic scenario to its logical extreme. It requires more than a half second of thought. Nothing in Dirty Grandpa appears to have been thought out any further than “what’s the grossest thing we can have Robert DeNiro say right now?” It is depressing, sure, but not because of the style; it’s all about the execution. I’m probably kidding myself that Robert DeNiro sticking his penis in the face of a sleeping Zac Efron is ever a joke that could be executed properly. It’s a joke that should probably be executed in the public square.

2. The plot of Dirty Grandpa is so thin that it appears to have been written on note cards that were thrown at the actors as they walked though each particular scene. DeNiro plays Dick Kelly, whose wife dies when the film begins; he requests that his grandson Jason (Efron) drive him from Georgia to Florida, for reasons I frankly don’t remember and do not care to. Turns out, Grandpa just wants to get to Daytona Beach so he can have a lot of sex and take a lot of drugs. No real reason is given for this other than “it’ll be funny to watch Robert DeNiro take a lot of drugs and curse and toss around millennial slang.” And let me tell you, reader, that is an awfully bad reason. Along the way, they come across a couple of spring breakers (Zoey Deutch—the daughter of Lea Thompson, which made me feel sort of old—and Aubrey Plaza, who I suspect initially thought she was signing up for a far different movie) and end up taking a lot of bong hits with their shirts off while drawing penises on each other’s faces. I could go on with the plot summary here, but why put us both through that?

3. Where do I start here? DeNiro’s Dick Kelly isn’t a character so much as a constant spewer of “outrageousness,” the outlet of the screenwriters’ desperate desire to offend everyone possible in the least inventive way. Kelly is sexist and homophobic and racist—Dirty Grandpa actually has a “comedic” section about the n-word that made me want to crawl under my chair, and maybe even curl up and die down there—but not in any sort of foundational, believable way. It’s not a character trait, or something that makes any sense in context, or out of it. DeNiro is just a puppet through which the filmmakers funnel every wretched, gross joke they can come up with. That’s depressing for DeNiro, but he gets no dispensation here: It’s depressing to watch, too. This frat house humor can be done well, or at least better; I (sort of notoriously) can’t stand the films of Seth MacFarlane, but at least his (nearly as bad) jokes take the form of jokes, with cadence and timing and the occasional set up. Here, DeNiro just spews and spews and spews, to no end other than to “shock.” If you are offended, you just don’t get it. And all told, the movie can’t even muster enough energy to rise to the level of offensiveness. I’m reminded of that old Onion bit about Marilyn Manson going door-to-door screaming, “Look at me, suburban dung!” and bathing in pig’s blood as residents take pity on him. Of course, it is one thing for Marilyn Manson to be the butt of that joke. It is quite another for Robert DeNiro to be.

4. While there is a temptation to lament what DeNiro puts himself through in this movie—and there is much to lament—it is worth noting that it does no other actor any favors either. The movie is so poorly thought out and shoddily constructed that the only reason I can imagine most of the actors signed up for it was because DeNiro was in it, and they trusted he had some idea what he was doing. (He didn’t.) Efron was funny and even a little charming in a lunkheaded way in Neighbors, but an attempt to recreate that magic here is a disaster. His willingness to go all the way for a joke is commendable—he spends most of the movie naked and/or with penises drawn on his face—but here he just goes all the way off the cliff. But the true victim here is Aubrey Plaza, so funny and sharp and acerbic in just about everything she’s ever been in. You can see what the idea was for her being in this movie. Her character is a Daytona Beach version of her usual type, an anarchist nihilist embracing the void, with the void being, in this case, the film-long journey to have wild sex with DeNiro’s grandpa. (“I want you to tear me open like a social security check.”) Plaza tries to have fun with this lunatic, and you can see the seedlings of what might have even been chemistry with DeNiro, were this a different movie with different people in charge of it. But here, it’s just a nightmare for her. My best hope is that it is a Joaquin Phoenix-esque I’m Still Here stunt she’s pulling on all of us, and she’ll show up on Colbert tonight or something and let us know she was just messing around. “Can you believe I was in Dirty Grandpa? What a prank that was!”

5. The film has such an awkward, halting, inept rhythm that one wonders how much of it was stripped apart and reconstructed in postproduction. It has the feel of a movie that had many doctors trying to save the patient on the operating table, failing, and then just throwing all the body parts inside the corpse, sewing it up, and hoping no one notices the patient’s dead. There is nothing wrong with crude humor in movies. This movie exists, surely, because of the success of recent gross-out comedies like Neighbors, The Hangover, or even Bad Grandpa, which is not a prequel to Dirty Grandpa but is in fact a lot better. (And it’s not even that good.) But you have to start with the jokes and then bring the penis drawings and the semen stains. Dirty Grandpa will make you feel bad for Robert DeNiro, and Zac Efron, and Aubrey Plaza, and the rest of the stranded cast. But it will also make you feel bad for yourself, and anyone else who sees it, and anyone else who has to live in the world where it exists as a physical document. It inspires despair for us all, for all of it.

Grade: D-.

Grierson & Leitch write about the movies regularly for the New Republic. Follow them on Twitter @griersonleitch or visit their site griersonleitch.com. Listen to their film podcast below.