Greg Heffley, the kid who made “wimpy” cool, is looking forward to his summer vacation in “Diary of a Wimpy Kid: Dog Days” but when his dad (Steve Zahn) decides they should spend more time together, Greg does everything he can to keep his father from ruining his summer vacation.

In “Diary of a Wimpy Kid: Dog Days,” which combines elements of both the third and fourth of the “Wimpy Kid” books, the good news is that school is out for the summer and Greg is looking forward to a vacation spent playing video games, hanging out with his best friend, Rowley, and working his way into the affections of the girl he has a crush on, Holly Hills. The bad news is that Greg Heffley being Greg Heffley, nothing is going to go as planned.

“At the start of the film Greg’s dad takes away all of his video game privileges and basically decides Greg should spend all his summer hanging out with him and doing outdoor stuff like camping and swimming,” explains Zachary Gordon, the thirteen-year-old actor who plays Greg.

In school or out of school, Greg also has a tendency to get himself into painfully embarrassing situations; Zachary says that this time round his on-screen alter ego plumbs new depths of humiliation. In “Dog Days”, Greg goes one step further and loses his swimsuit in a crowded pool. Greg also has what Zachary delicately refers to as a “mishap” on a roller coaster, meaning, we’re pretty sure, that Greg throws up on his fellow passengers. For the record, Zachary admits he was a bit nervous himself when it came time to shoot the film’s roller coaster scene but after a couple of time around, he was hooked. “I went on six times in a row,” the young actor says, “It was awesome.”

“And playing Greg for a third time, I feel like I settled into it as soon as I saw the rest of the cast again. It was more like a ‘Wimpy’ reunion than coming back to work,” Zachary says, “because everyone feels like part of my family now.”

“Diary of a Wimpy Kid: Dog Days” will open August 15 in theaters from 20th Century Fox to be distributed by Warner Bros.