I'd never be one to accuse the "Jackass" guys of doing something half-assed. After all, these are the same guys who launched themselves into the sky on a rocket and did innumerable terrible things to the most delicate parts of their bodies (even in 3-D!), all in the name of gleefully juvenile entertainment. But besides an Oscar nomination-caliber fart joke (they give out Oscars for fart jokes, right?), "Bad Grandpa" never quite reaches fever pitch.