Continuity mistake: When Samantha is being introduced to the class, there is a boy in The Front row on the right side that is wearing a white shirt and has brown hair. A few shots later (an overhead shot of the classroom), the boy is completely different, with a blue shirt and white hair. (00:04:00)
Continuity mistake: Before Marge sees Homer parking violation, if you look at where he is parked over the first handicapped spot there is a car parked in the first non-handicapped spot. A bit before Marge arrests him there is now a non-handicapped spot between the car and Homer's car. (00:14:35 - 00:15:05)
Continuity mistake: After Marge's left pocket rips in the candy convention, she goes to start picking up the candy when we see that the right pocket has ripped all of a sudden. When Homer and Marge start running away the pockets are no longer ripped and full of candy again.