During the town meeting scene, the position of Latin jazz great Tito Puente hops all over the room, frequently appearing in the background but from various angles.
The Burns Slant Drilling Corporation sign changes every time the building is shown.
When we first see Marge right around the time Mr burns was shot she didn't have Maggie in her arms however only a real short time later when he falls on the sun dial shot she does have her in her arms.
When Krusty first arrives at the Town Hall he is wearing an open collar, but when everyone is gathered around the sundial he has a bow tie.
Mr. Burns' sun-blocking disc would only work for a few minutes per day while the sun was in a certain position in the sky, since the disc was only as big as the visible sun itself. It would have had to be several miles across like the gigantic spaceships in "Independence Day" and "V".