Do to the fact that the actors are growing up it was necessary to make movie #3 the last movie. However they knew "The Last Straw" and "Dog Days" where fan favorites. They did NOT skip "Last Straw" at all. They decided to combine the books "Last Straw" and "Dog Days" into one movie instead of two, since there was not the time or money to film one then show it, then film the next one. The idea is that part of the movie (Last Straw part) would take place at the end of a school year, and the other part (Dog Days) takes place during the summer. Because the other two movies took place during the school year, they wanted this one to be different and be during the summer mostly. Also, the actor who plays Greg, Zachary Gordon (who is a genius actor) is now a teenager and his voice is changing, so they wanted to make the movie set in a part of the series where people wouldn't think "Gee, he's only supposed to be 12, he sounds 13, booo!"