To add to the "DW's Age" observations, Emily is already 5 in "D.W.'s Perfect Wish", but "D.W. Bossy Boots" shows her 5th birthday party, so that episode takes place before D.W.'s Perfect Wish (and that's ignoring the fact that Emily had her newer look there, of course).

In "Buster's Amish Mismatch", Brain says that there's a "lack of farmland in the area". Though there are at least three episodes that show farmland that is suggested to be close to Elwood City: the insanely long line to get Binky tickets in "Meet Binky", the end of "Buster's Carpool Catastrophe" (the cooking class couldn't have been that far away), and when Buster tells George he's 2/3 of the way to Elwood City from Crown City in "The Long Road Home".

And another calendar/school inconsistency: In "The Long Road Home", George has his walk scheduled for July 26 on his calendar, but there are scenes that take place in school that same week.