Gilbert Gottfried used to do a stand-up tour where he just did dirty public domain jokes for an hour, occasionally interrupted with an unfunny impression. I always thought he was kind of a hack for it, because what's the merit there? It's not like you have to go to bars and collect dirty jokes like gems, there are plenty of books and websites on the subject. As embarrassing as that tour/DVD was, at least a guy standing on a stage is the correct medium for that sort of thing. These jokes are meant to be told, not acted out in "sketches". In one of the few tie-in scenes that are put in this movie to give the illusion of a plot, one character actually mentions how a movie that's nothing but old public domain jokes would suck. Yes, it will and it does, why make it then? Pointing out your errors as an in-joke doesn't get you off the hook, it usually makes everything worse. There are two credited writers/people who know how Google works, and the parts where they are forced to come up with new jokes are among the most embarrassing movie scenes I've ever witnessed. The pre-credit sequence is a girl that sings the national anthem, but the joke is that her singing is off-key. There's no punchline and the scene goes on forever, is this just put in to make you long for the parts with old jokes everyone already knows?
The worst part of the movie has got to be the child actors though. The entire point of casting children was just for shock value (children swearing was apparently still edgy in 2011), but they're clearly reading their sex jokes from cue cards and still mess up the punchlines. They often sound like they don't even get the joke, putting the emphasis on the wrong words and things like that. Chances are they'll be pretty embarrassed by this movie once they've grown up, and perhaps they should be.