From its origins as a series of online cartoons, “Diary of a Wimpy Kid” exploded onto the pop culture scene when Jeff Kinney’s first “novel in cartoons” was published in 2007.

“Diary of a Wimpy Kid” spent almost three years on the New York Times’ children’s bestseller list. There are 75 million copies in print in 37 languages.

The book captured the imaginations of an army of formerly “reluctant readers,” and launched countless video reviews, social networking fan groups and parties celebrating the release of each new “Wimpy Kid” book.

The first motion picture, based on Kinney’s debut “Wimpy Kid” novel, brought to cinematic life the adventures of wisecracking pre-teen Greg Heffley, who must somehow survive the scariest time of anyone’s life—middle school.

In the second picture, “Diary of a Wimpy Kid: Rodrick Rules,” which opened as No. 1 at the box office, Greg and his older brother and chief tormentor, Rodrick, deal with their parents’ misguided attempts to have them bond.

In the new film, Kinney (returning as executive producer), director David Bowers, producers Nina Jacobson and Brad Simpson, and screenwriters Maya Forbes and Wally Wolodarsky, focus on the father-son relationship of Frank and Greg Heffley, as played by Steve Zahn and Zachary Gordon.

School’s out, rules are out

School’s out and Greg is looking forward to enjoying the best summer of all time.  But when his dad decides that some father-son bonding is in order, Greg must do everything he can to keep him from ruining his vacation.  So he hatches a plan to pretend he has a job at a ritzy country club—but even that fails to keep Greg away from the season’s dog days, including embarrassing mishaps at a public pool and a camping trip that goes horribly wrong.

“Diary of a Wimpy Kid: Dog Days” follows Greg Heffley’s summer adventures—from the comfy confines of his living room, where all he wants to do is play video games; to the aquatic frenzy of the local municipal pool; to the plush and leisurely luxuries at a lavish country club; and to a wild camping trip outside of the familiar comforts of suburbia.

“Summer vacation and childhood are deeply associated,” says Jacobson.  “When you’re a kid, there’s nothing you look forward to more.”

David Bowers adds, “I think summer vacation is a great source of comedy because often people have plans and look forward to it, but it isn’t always as awesome or amazing as you hope it might be.  And that certainly is the case for Greg, whose vacation might not be as much fun as he thinks it should be.”

Returning cast members also include Robert Capron as Greg’s best friend, Rowley Jefferson; Devon Bostick as Greg’s brother, Rodrick; Rachael Harris as their mom, Susan; and Peyton List as Holly Hills who is Greg’s summer dream.

Based on books

“Diary of a Wimpy Kid: Dog Days” is based on Kinney’s third and fourth “Wimpy Kid” books, “The Last Straw” and “Dog Days.” Kinney, who worked closely with the screenwriters, producers and director, says, “We have an obligation to our readers, to make sure we’re protecting their expectations and don’t stray too far from the books.”

At the same time, Kinney points out the movie adaptations are not carbon copies of the books.   He likens the adaptation process to the experience of and expectations for attending a pop music event: “It’s kind of like going to a concert of your favorite band.  You wouldn’t really enjoy it if the band just played the songs from its latest album, in order—why not just stay home and listen to the album?   So you try to mix up the playlist a little and play a new song, maybe a cover song from somebody else. That’s the same model we have for the movies: we try to give fans enough to meet their expectations, but also add new elements to surprise them.”

“Jeff really is the glue that holds the films together,” says Simpson.  “His presence on the set was very important to the cast.  He helps keep the integrity of the books on the screen.  Jeff is part of the fabric of the films in an intense and amazing way.”

Jacobson adds: “Jeff’s role has been to be the guardian of the ‘Wimpy Kid’ voice.  He is our go-to guy when we need a great joke, or when we need to check whether a character would really do something.”

“The books are popular because they’re told from a kid’s perspective and they’re clever and honest, don’t talk down to readers and really capture the angst of being a kid and what’s important to you at that age. I think the movies are good because they’ve been able to do exactly what the books have done. They’re funny and smart and real. My own kids love these films. In fact I think it’s the first thing I’ve done that’s really impressed them,” concludes Zahn.

“Diary of a Wimpy Kid: Dog Days” of 20th Century Fox will open on Aug.15. It is distributed by Warner Bros.