Without any "Based on..." mention in the credits or even a surprise cameo by Chevy Chase, "Johnson Family Vacation" is just a chintzy, plagiaristic redux of 1983's classic "National Lampoon's Vacation." There is even a moment, involving the singing of a particular Wayne Newton song, that is a blatant steal from 1997's "Vegas Vacation." Let's just say that when you find yourself reaching for inspiration from the weakest entry in an otherwise successful four-part series, you know you're in real trouble. Appallingly unfunny, to boot, there isn't an original, witty, or genuine moment to be found in the entire, seemingly never-ending 96 minutes of "Johnson Family Vacation."

Nate Johnson (Cedric the Entertainer) is a mild-mannered Los Angelean who sets off on the open road with his family in a newly-rented, pimped-out Lincoln Navigator. On their way to Missouri for their extended family's annual reunion, where the distinguished title of "Family of the Year" has been just out of reach in years past, Nate also hopes to rebond with estranged wife Dorothy (Vanessa Williams) and spend quality time with aspiring rapper son D.J. (Bow Wow), cell phone-obsessed daughter Nikki (Solange Knowles), and precocious tot Destiny (Gabby Soleil). As with Clark Griswald's misadventures, everything that could go wrong for Nate and family does. A psychotic trucker tries to run them off the road. A luxurious dip in the hot tub ends with Nate being bombarded by hefty, buxom strangers. When they make the mistake of picking up sexy hitchhiker Chrishelle (Shannon Elizabeth), they learn too late that she is a voodoo witch. Their SUV is virtually destroyed by wet cement, and then they run out of gas in the middle of nowhere. Unlike Clark Griswald's misadventures, however, none of it is the least bit funny or fresh. Furthermore, the Johnson family is an insufferable, one-dimensional lot—a far cry from the likable Griswald clan.

The shoddy directing debut of Christopher Erskin, watching "Johnson Family Vacation" is about as stimulating as an actual 300-mile drive across the desert wastelands of Arizona and New Mexico. The film's goals are simple enough to figure out—it wants to be a light, comic entertainment with slapstick moments culminating in a well-meaning, moralistic ending—but it fails at all of the above. Frothy though it may be, the picture is a veritable chore to sit through, its every worn-out, groan-inducing setpiece taking twice as much time as it needs to set up a joke that can be seen coming a mile away by any viewer with half a brain.

The horridly banal screenplay (by Todd R. Jones and Earl Richey Jones) is to blame for the film's plodding, lazy nature, but so is the editing by John Carter (2002's "Barbershop"), who doesn't show any proof that he can adequately set up a joke through the rhythmic buildup of his shots. There is a difference between carefully milking a comedic moment for all it's worth and dragging said sequence out so far beyond the limits of possible impact that it just tests one's patience and feels desperate. Other comedy bits, such as the placement of a payphone in a cornfield and a nonsensical sign the family passes advertising the reunion, are so outlandish and nonsensical that they feel like they should be in a different movie altogether. Because there is only one marginally funny scene in the whole film, concerning an unorthodox dinner prayer given by Chrishelle, the overly deliberate pacing isn't only annoying, but close to unbearable.

The characters, and the cast who play them, are just as poorly managed. Cedric the Entertainer (2004's "Barbershop 2: Back in Business") is more low-key than usual, but he has little to do but react to the hilarity around him as Nate Johnson. Vanessa Williams (2000's "Shaft") makes put-upon, scowling faces as wife Dorothy, all the while rekindling her love for Nate. This romantic subplot isn't believable for a second. As for teenage son and daughter D.J. and Nikki, Bow Wow (2002's "Like Mike") and newcomer Solange Knowles (Beyonce's younger sibling) are simply terrible, mistaking exaggerated body gestures and line readings for a true performance. There is no depth to D.J. and Nikki, nor is there any palpable connection made between them as brother and sister, or between them and their parents. The hitchhiker subplot had quirky potential, but Chrishelle, her witchcraft, and the possible circumstances concerning spending time with her are never explored. Director Christopher Erskin simply rushes through this segment and abruptly disposes of Chrishelle, who is more interesting than any of the leads, without satisfying closure. Shannon Elizabeth (2001's "American Pie 2") is better than her thankless role gives her credit for.

When the Johnson's finally arrive at their family reunion in Missouri (let it be known it looks more like the Hollywood Hills than the Midwest), it is understandable for the viewer to expect the story to wind down. Instead, it continues on for another interminable half-hour, complete with grating arguments between Nate and snotty big brother Max (Steve Harvey), a potato sack race, and a talent show featuring two musical performances. Ultimately, Nate and his family learn a thing or two about the importance of being there for each other no matter what, and they quickly scurry on back home. The epiphany Nate experiences may mean well, but the way it is presented is egregious and sickeningly corny. It doesn't help that we have never grown to care about the Johnson family, either as individuals or as a whole. We're just glad when our time with them has reached an end.

Speaking of the end, it doesn't come nearly soon enough in "Johnson Family Vacation," a vacuous comedy questionably too racy for young children but not mature enough for anyone over single digits. This very conundrum, mixed with blatant copycatting of the superior "Vacation" movies, amateurish production values, and egotistical preaching, sinks the film faster than a coin dropped into a water fountain. "Johnson Family Vacation" is wretched, indeed, notably more loathsome than could have even been expected.