1. They try to sneak lessons in the books. The author started doing this in either book 4 or 5, but it's really annoying. If it's supposed to be written by kids, it would likely not have a moral. I think this is a move forced by Scholastic/Graphix, the publisher.
2. Petey is a good guy?! Petey was a perfectly fine villain, and then Li'l Petey came in and somehow made Petey a good guy.
3. Why is it called Dog Man, if it's about Li'l Petey? Unlike what the title says, Dog Man is not the main character in the newer books. It's more about Li'l Petey and Petey, who's facing problems with becoming a good guy and Grampa. Li'l Petey has his own book series, and he's the least important character in that series.
I'm hoping that the author retcons book 5-11 or reboots the entire series.