In the scene right before Rowley asks Greg if he "Wants to come over and play", Greg walks out, and you see a girl walking down the stairs behind him. When they show Rowley, the girl is again seen coming out of the school.
When Greg first enters class on the first day of school, Greg Heffley is written on the blackboard. In the next shot, it is gone. In the shot after that, he writes his name on the board.
Greg takes Manny off the toilet, who leaves on the right. Susan is carrying Manny, but she comes from the left.
Some of the foam from the fire extinguisher is sprayed onto Greg. Two shots later, Greg is clean.
After their first meeting with Angie under the bleachers, Greg makes an excuse about hearing the whistle signaling the end of P.E. class before dragging away Rowley by grabbing his right wrist/hand. But in the next shot as they retreat, Greg is shown leading Rowley by the left wrist, not the right.
Just before Greg's dad tells him it's 4:00 am he looks at his wrists though neither wrist has a watch.
Greg's dad was being sarcastic and was making a point and it's known he checked the time before going into the kitchen.
Greg's dad was being sarcastic and was making a point and it's known he checked the time before going into the kitchen.
When Greg opens the school door at the start of the movie, a trash can is knocked over and it is completely full. This scene was set at the very beginning of the school year, making a full trash can seem strange as they would have been emptied over the summer.
When Mr. Heffley dumps water on Greg and Rowley from the roof, mistaking them for teenagers, it's blatantly obvious that someone simply threw the water at them from off-camera.
Greg goes down on his popularity chart from 19 to 72. The 19th place would then be vacant. Rowley later fills the 19th spot. Greg later goes down from 72 to 202. The 72nd spot is vacant, but it is not filled because Greg is in spot 202 of 201.
A normal drama teacher, when faced with only a few kids who can carry a tune vs many that can't sing, would never worry about someone's voice being too high for a role. They would cast those who can sing well in the large parts regardless of how high their voice is.
In the scene where bullies attack the school yard, a girl in the backround can be seen slowly slipping off her sandal and in the next shot she completely loses it. She then runs away with the crowd and isn't seen again. This makes no sense for the movie and is likely just the actress getting comfortable or something.
When Rowley hands Greg the Zoo Wee Mama comic he says "I put you in the comic this week." It's just the one with the acid puddle and squirrel with no change from the original drawing he made at Greg's house.