My hopes were high for “Dirty Grandpa,” simply because its mere existence made no practical sense. A movie starring Robert De Niro and Zac Efron doesn’t sound like a real movie. It sounds like a fake movie you’d see clips of in a film that’s mocking the stupidity of Hollywood. For all intents and purposes, “Dirty Grandpa” should only exist in the form of one of the fake trailers that open “Tropic Thunder.” And yet, here it is. All 102 minutes of it.

Before watching this, my mind raced with all of the stupid possibilities. How many Viagra jokes would there be? Would somebody ask De Niro about his Viagra induced boner and have De Niro respond, “Are you talking to me?” shortly before one of the grips runs onto the set to give him a high five? Would there be a scene in which a dog wins a farting contest after it farts so hard it launches itself inside of the bare, gaping ass of its competitor: a cameo by Harvey Keitel (who, it’s implied, accidentally overdosed on Viagra)? Unfortunately, these moments were not to be – outside of my Pinterest page and/or dream board. But luckily, what we got was equally stupid. Maybe even a little more so.

As you may have already guessed, “Dirty Grandpa” is as terrible as its derivative title implies. But “Dirty Grandpa” is also the kind of terrible I can embrace and appreciate. It’s bad but in a way that might be intentional. Ten minutes into the film we’re greeted with the sight of a nude, 72-year-old De Niro graphically masturbating to a porno movie. Was this grotesque gag supposed to make us laugh? Or was it an attempt at Tim & Eric-style anti-comedy? It’s hard to say. But considering that “Dirty Grandpa” was directed by former “Da Ali G Show” scribe Dan Mazer, it could possibly be the latter.

“Dirty Grandpa” is an extremely low stakes road comedy with a plotline so tossed-off and vaguely defined that it makes the aimless, improvisatory “Bad Grandpa” look nuanced and densely plotted. In the movie, De Niro plays a dick joke that walks like a man (almost literally. His character’s name is Dick Kelly for Christ’s sake) who gently coerces his uptight grandson (Efron) into driving him down to Boca Raton. Ostensibly, it’s because the recently widowed De Niro wants to reconnect with an old army buddy, but in reality it’s because he totally wants to ‘get it wet’ and help his buzzkill of a grandson to break free from his future ball and chain (The very Nordic Julianne Hough inexplicably cast as an offensive Jewish American Princess stereotype) and his domineering father (Dermot Mulroney).

And then – well, that’s pretty much it. But who cares about story when you have De Niro croaking out a cover of Ice Cube’s “It Was a Good Day” or screaming labored, improvised insults like “Cocky McBlockerson” into Efron’s unfeeling, porcelain face (he basically looks like the doll from “The Boy” if it was 60 percent abs)?

Some critics have defended De Niro’s late period career choices by noting the “realities of remaining a working actor into old age” without acknowledging that De Niro really doesn’t need to be a working actor anymore. He could have pulled a Jimmy Cagney and comfortably retired as a respected private citizen instead of now being known as the guy who played the guy who screamed about what it would be like to have Queen Latifah defecate in his mouth from a hot air balloon. But it’s exactly this sort of schadenfreude that makes “Dirty Grandpa” so seductive.

Seeing the star of “Mean Streets” and (sadly) “The Adventures of Rocky and Bullwinkle” play a less funny, more racist version of Danny DeVito’s character from “It’s Always Sunny in Philadelphia” is something that must be seen and cherished. Additionally, “Dirty Grandpa” is so stupid and gleefully filthy that you’ll find yourself laughing in spite of yourself.

Danny Glover cameos as an infirmed old man who gets a little too excited by a violent episode of “Alf.” Aubrey Plaza blows a bong hit into De Niro’s mouth shortly after he nearly kills a kid with a T-Shirt gun. Jason Mantzoukas and Henry Zebrowski play a pair of unrepentant but cheerful Florida scumbags. “Dirty Grandpa” is so ill-advised, incompetently made and singularly weird that it must be seen at least once. After all, De Niro has nowhere else to go but up at this point. Enjoy rock bottom while it lasts.

“Dirty Grandpa”

Starring: Robert De Niro, Zac Efron, Zoey Deutch

Director: Dan Mazer

Rated: R

Weekender Rating: WWW

Length: 102 min.

Mike Sullivan is a movie reviewer for Weekender. Movie reviews appear weekly in Weekender.

Story lacks originality but brings laughs

By Mike Sullivan | For Weekender

This photo provided by Lionsgate shows Zac Efron, left, as Jason Kelly and Robert De Niro as Dick Kelly in the film, “Dirty Grandpa.”
https://www.theweekender.com/wp-content/uploads/2016/01/web1_EfronDeNiro.jpgThis photo provided by Lionsgate shows Zac Efron, left, as Jason Kelly and Robert De Niro as Dick Kelly in the film, “Dirty Grandpa.” AP photo

This photo provided by Lionsgate shows Zac Efron, left, as Jason Kelly and Robert De Niro as Dick Kelly in the film, “Dirty Grandpa.”
https://www.theweekender.com/wp-content/uploads/2016/01/web1_DeNiroEfron.jpgThis photo provided by Lionsgate shows Zac Efron, left, as Jason Kelly and Robert De Niro as Dick Kelly in the film, “Dirty Grandpa.” AP photo

This photo provided by Lionsgate shows, Zoey Deutch, from left, as Shadia, Jeffrey Bowyer-Chapman as Bradley, and Aubrey Plaza as Lenore, in the film, “Dirty Grandpa.”
https://www.theweekender.com/wp-content/uploads/2016/01/web1_ClubScene.jpgThis photo provided by Lionsgate shows, Zoey Deutch, from left, as Shadia, Jeffrey Bowyer-Chapman as Bradley, and Aubrey Plaza as Lenore, in the film, “Dirty Grandpa.” AP photo