The Original Movie: 86-year-old Irving Zisman (Johnny Knoxville, in Oscar-nominated old-man make-up no less) goes on a road trip with his 8-year-old grandson, Billy (Jackson Nicoll), in order to return him to his father, but of course, the pair get in a ton of lewd shenanigans along the way. The Ripoff: A perverted, former Army general, Dick Kelly (Robert De Niro), tricks his soon-to-be-wed, uptight grandson Jason (Zac Efron) into driving him to Florida for Spring break. Again, lewd shenanigans ensue no doubt. They weren't even trying to mask this one at all: hell, the title's damn-near identical, and given that they both revolve around horny old men roping their suffering grandsons into a ridiculous set of scrapes, it doesn't sound like the filmmakers much care. Bad Grandpa did make over $150 million at the box office (more than 10x its budget), so perhaps it's no surprise that Lionsgate are playing it so safe with both their title and premise.