It seems only fitting that the last sound the audience hears in "Fun Size" before the end credits roll is a poop dropping into a toilet. The sad plop of fecal matter into water is the closing moment that director Josh Schwartz chose to send audiences out hopefully smiling and laughing. Instead, it serves as the final annoying punctuation to a previous 85 minutes of confused, exhaustingly "zany" and inept comedy. As Nickelodeon TV star Victoria Justice's first big-screen star vehicle, it's a Yugo.

Justice (cute but Disney Channel-brand generic) plays Wren Desantis, a chipper young Cleveland high school student who's planning on heading out of "the mistake by the lake" for NYU. This doesn't please her mother (Chelsea Handler), who's in the midst of a midlife crisis – mainly consisting of dating a college student who lives at his parents' house – due to her husband's sudden death. Raising a little hellion son Albert (Jackson Nicoll) probably doesn't help matters.

All the drama comes to a head on Halloween night, when Wren has to babysit Albert instead of going to the neighborhood hottie's (Thomas McDonell from "Prom") party. Of course, she and her requisite snarky comic relief best friend (Jane Levy, next to be seen in the "Evil Dead" remake) lose the tubby little prankster and must scour the city to find him.

Along the journey, they fall in with cliché nerds (Thomas Mann as the sweet inevitable romantic interest nerd, Osric Chau as the horny Asian nerd) and run into numerous other stereotypes along the way, including a bunch of 'roided up bullies and Mann's super left-wing lesbian parents. At one point, they have to borrow Mann's moms' prized car and promise not the scratch it. What could possibly happen to this automobile? Will "Fun Size"'s comedic innovation ever cease?

Nope, and Albert's adventures with a revenge-seeking gas station attendant (Thomas Middleditch, providing the film's few laughs) don't provide much more relief. It's just another set of tiresome hijinks – mainly featuring a Sumo wrestler and Johnny Knoxville – with predictable results.

Schwartz and writer Max Werner are clearly going for a '80s teen comedy vibe in the vein of "Sixteen Candles" and "Adventures in Babysitting." However, instead of taking the combination of heart and zaniness that made those movies classics, "Fun Size" bombards the audience with ridiculous scenarios and cheap jokes.

Near the end, the movie tries to pull a last-ditch effort to tug on some heartstrings, but after an assault of charmless fart jokes, poop jokes, boob jokes and humping jokes – an extended one featuring a giant mechanical chicken – it's completely unearned.

Parents may be surprised to hear that roll call of crass content, and I wouldn't blame them. It's a Nickelodeon production starring a Nickelodeon starlet whose entire career up to this point has been kid-friendly. The official MPAA rating wasn't widely known either by the time of its release. Sneakily done, Paramount.

Frankly, though, the whole movie seems confused about the adult content. Half of the film wants to be a silly kids' adventure; the other half wants to be raunchy for the older crowd. It's an identity crisis that makes watching "Fun Size" far more awkward than need be. The adult jokes – an extended gag about using Nair on one's posterior, plenty of profanity – are uncomfortable, and the childish stuff – goofy dancing, all the pooping and farting – seems even more childish. There's also an auto-tune joke, though I'm not sure what audience that's for. Maybe people finally getting around to memes from two years ago.

It's all about as pleasant as finding a razor blade in your Snickers bar and just as safe for kids.