'Dirty Grandpa." The un-ironic title is like a spray-painted graffiti sign warning everyone to stay away from this sewage-swilling clogged cesspit masquerading as a movie. Woe betide anyone who catches this on an airplane, they may wind up using all the airsick bags in their row, because it really stinks.

The burning question that pops up two minutes into "Dirty Grandpa" has to be: Why doesn't Hollywood treat its iconic stars with more respect? Two-time Oscar winner Robert De Niro, who has given us some of the most memorable characters in American cinema (Vito Corleone in "Godfather II," Jake La Motta in "Raging Bull," Al Capone in "Untouchables" to name just a few), stars as Dick (I'm not kidding) Kelly, a retired U.S. Army general who just lost his wife of 40 years.

In what feels like a mere seconds after the funeral, Dick is already masturbating to a porn movie, and when his grandson Jason (Zac Efron) walks in on him, he merely remarks that he's almost done, without a trace of embarrassment. That's not even a low point of the film, that's just director Dan Mazer ("I Give it a Year") flexing his arm muscles to throw s—- pies at the audience and, by implication, at De Niro who's widely acknowledged as one of the greatest actors of all time.