2010's "Diary of a Wimpy Kid" was episodic and lightweight, but within its loose narrative structure was an exploration of the frustrating, frequently stressful middle school experience that rang mostly true, despite its PG rating. In "Diary of a Wimpy Kid: Rodrick Rules," the characters from Jeff Kinney's best-selling book series are all back, a year older but not exactly wiser. Whereas its predecessor spanned the length of one school season, this spottier first sequel has no such blueprint to follow. It begins at the start of the seventh grade for underdog hero Greg Heffley (Zachary Gordon), but then meanders around from one broad, usually strained set-piece to the next until it runs out of material and just ends. There are diverting moments, to be sure, but director David Bowers (2009's "Astro Boy") and returning screenwriters Gabe Sachs and Jeff Judah simultaneously try too hard and not hard enough, going for slapstick scenes of humiliation more mean than funny and forgetting to add up to any sort of gratifying catharsis. No one really learns anything this time out—about life, or growing up—making it a faint shadow of the original.

Before Westmore Middle is even back in session, 12-year-old Greg Heffley has laid eyes on lovely new-girl-in-town Holly Hills (Peyton List) at the roller skating rink and fallen helplessly for her. Almost everyone, including Greg's vicious teenage brother Rodrick (Devon Bostick), tell him he's dreaming if he thinks he might have a chance with her, but that's not about to stop him from trying. Meanwhile, Greg's mom (Rachael Harris) has begun writing an advice column in the local paper called "Susan's Musings" and is determined for her two bickering eldest sons to finally get along. What she proposes—giving them each a dollar ("Mom bucks") for every hour they spend together in harmony—is well-meaning, but Rodrick immediately starts abusing the process while pulling the wool over his mom's eyes. As Rodrick cruelly tells Greg, "You may be my brother, but you'll never be my friend."

The chief problem with "Diary of a Wimpy Kid: Rodrick Rules" can be found in the title. Simply put, Rodrick is an insufferable creation, an obnoxious, cruel, unamusing prick of a character who treats his family—especially Greg—with an appalling level of disrespect and doesn't appear to have a sympathetic bone in his body. He's a total oaf, using his mother for money without a tinge of affection for her and doing things to Greg that range from embarrassing to potentially criminal. Rodrick shames Greg in front of the entire congregation at church, he blackmails him with a surveillance video of Greg running around a senior center in his underwear after his diary is stolen, he locks him—and later Greg's best friend Rowley (Robert Capron)—in the basement while he throws a party, and he's never anything less than awful to him when they could be getting to know each other better. The film's eventual message about the importance of being close with your family is all but lost due to Rodrick's reigning disingenuousness. There is a half-hearted scene at the very end where Rodrick kinda-sorta thanks Greg for a selfless act he performs, but it's too little and far too late. Yes, we all get into occasional tiffs with our siblings, but there doesn't appear to be any love whatsoever in Rodrick's heart for Greg. It's a gravely wasted opportunity for a movie that had the perfect chance to really portray the unbroken bonds between brothers.

Nearly the entire cast has returned from last year's "Wimpy Kid" with the exception of Chloe Grace Moretz, who has since gone on to bigger and better things and whose character of Angie Steadman isn't even mentioned. Zachary Gordon reprises the lead role of Greg Heffley with spunk and a more learned comic handle. It is Robert Capron (2010's "The Sorcerer's Apprentice") as fiercely loyal best friend Rowley Jefferson, however, who is the scene-stealer. Lovable, earnest and reliably humorous—his lip-synching to Ke$ha's "Tik Tok" is a highlight—Capron has what it takes to grow into a truly talented actor, the kind that breezes through comedy and seems to always find the heart underneath. As Greg's mom Susan, Rachael Harris (2009's "The Hangover") gets more to do this time since the focus is on the family rather than at-school antics, though Steve Zahn (2009's "A Perfect Getaway") still hasn't gotten his moment to shine as father Frank. As Rodrick, Devon Bostick (2009's "Saw VI") does what is asked of him, but tends to go overboard. Still, it's not solely the actor's fault that Rodrick is thoroughly unpleasant to be around. Were his character kidnapped in the inevitable third film, his disappearance would come as sweet relief. New to the series is Peyton List (2011's "3 Backyards"), a sweet, unaffected presence as the subject of Greg's crush, the brilliantly-named Holly Hills.

For every sly little joke like Greg's confusion over how to use a rotary phone, "Diary of a Wimpy Kid: Rodrick Rules" is undone by failed gags and distasteful bathroom humor, including one scene where Greg is confused for a peeping tom after elderly ladies catch him in the women's restroom. Furthermore, the story—what there is of one—is overwhelmed by situational comedy skits. When director David Bowers finally gets down to making a point about sibling relationships, it lacks emotional sincerity and gets sheepish, anyway, about adequately developing Greg and Rodrick as anything but enemies. At the conclusion of "Diary of a Wimpy Kid," the viewer sensed that Greg and Rowley had genuinely grown as people over the course of their sixth grade school year. That's not the case here. "Diary of a Wimpy Kid: Rodrick Rules" is more concerned with tired punchlines and gross-out ploys than imparting any lasting insight.