It has been a while since Robin Williams has had a starring role in a pure comedy. He has recently proven his acting prowess in such films as "One Hour Photo" and "Insomnia," but it was only a matter of time before he fell back into what he does best.

Unfortunately, what he does best does not entirely show in "RV." Williams plays a white-collar workaholic and father-of-two named Bob Munro. This character would be a bit of a stretch for Williams dramatically and, here, is a damper comically. It severely limits the amount of his trademark zaniness.

The movie opens on a good note, showcasing Williams' delightful storytelling abilities. Bob is putting on a puppet show for his daughter, who is still a small child at the time. Her eyes light up while he ridiculously role-plays as the man who saves her from the dreaded "Tickle Monster."

Then, there is a flash-forward to about a decade later when he and his now-teenage daughter are having a typical father-daughter quarrel. Joanna Levesque, better known as pop singer JoJo, stars as his daughter, Cassie. She plays a one-dimensional, bratty teen who has lost the admiration for her father that she once possessed.

Bob had previously promised to take his family to Hawaii but soon his boss shoots down this planned vacation. During this time, he is instead needed in Colorado to finalize a merger.

Will Arnett, fresh out of brilliantly portraying Gob Bluth on "Arrested Development," brilliantly portrays Bob's boss, Todd. Arnett is a master of smugness. If he were typecast as this sort of character, it would be best for his career and for his fans. As a side note, Tony Hale, Arnett's "Arrested" brother Buster, has a small role as the co-worker that originally brings up the idea of taking a road trip in an RV.

Consequently, as a way of having his cake and eating it too, Bob decides to take his family on a trek to Colorado aboard a giant RV, arriving just in time to attend the meeting. The RV is a bright green eyesore with "Rent Me" humorously plastered across one side of it.

Bob's wife, Jamie (Cheryl Hines, "Curb Your Enthusiasm"), objects to the journey, pointing out that they are going to have to stay at RV parks and that their family is certainly not the friendly type. Soon, though, the Munros are on their way to Colorado.

Along the way, Bob's son, Carl (Josh Hutcherson, "Zathura"), notices that the toilet is backed up. Apparently, the previous renter of the RV had never emptied the waste tank. This leads to a scene of failed attempts at emptying to empty the tank, resulting in Bob getting covered in feces. This is not funny, nor is a moment like this in almost any movie. The thought or discussion of feces often can be funny, but once it is seen, disgust takes precedence.

On the other hand, some instances that are humorous involve Bob bumbling or trying to talk himself out of various situations. Most of these moments occur while trying to avoid the Munro's newfound and unwanted friends, the Gornickes.

The father of the family is Travis (Jeff Daniels, "Dumb & Dumber"), who is as friendly as he is naíve. His wife, Marie Jo (Kristin Chenoweth, "The West Wing"), is about as optimistic as a person gets. Daniels and Chenoweth exude such energy and sincerity with their performances, it is impossible not to like them and sort of feel bad when the Munros repeatedly ditch them. These attempts to avoid are still quite entertaining, though.

Another entertaining example is one that is also kind of surprising. At one point, Carl jokingly asks Connie if she is on the "South Bitch Diet." Bob promptly praises him with an impressed "Good one." This interaction is funny, but it is most of all shocking for a PG-rated movie. Perhaps this was not appropriate in a movie that is so intentionally targeted toward a younger audience. Then again, most of the audience has probably heard worse.

Worst of all is the end. The emotional turns are much too abrupt. Reasons for decisions in one direction and then suddenly changing one's mind in another are not well developed throughout the narrative, leaving these moments of change to come off as forced and empty. Yet, one could argue that being a family is reason enough.

Nevertheless, though the journey barely leads anywhere and no new ground is even attempted to be broken, "RV" has the kind of familiar charm that keeps the audience entertained for its 98-minute run. Simply put, "RV" is OK.

Rating: 3 out of 5