Other mistake: The doctor in the insane asylum shows a video that shows a child Ned Flanders from 30 years ago. Ned is 60.
Other mistake: When Ned Flanders is calling Marge and Reverend Lovejoy from the Leftorium, he says that the three hooligans are in the shop on their motorbikes. But a few minutes before when Ned goes outside the shop to tell the boys to clear off, their bikes are nowhere in sight.