When the Professor Membrane screen is saying, "Do you love me?" and waiting for the command input, the green button is on the left, and the red button on the right. In the next shot, the order is the opposite. It goes back to normal in the scene after that.
When Professor membrane's floating screen device gets stuck in 'Do you love me?' mode, the device has the green 'Yes' button on the left and the red 'No' button on the right. When Dib goes to push the button, they suddenly switch places.
When Willie and Zim were debating with the popularity brain-wave readers, there was a scene where the view switched between Zim and Willie. Zim's eyes were alien for at least three shots, and then his eyes went back to being disguised.
In the segment "The Voting of the Doomed", immediately after Ms Bitters tells the auditorium "Now comes the awkward silence part" the shot snaps between Zim and Willy. In this quick back and forth, Zim's 'human eye' lenses are suddenly absent.
During the "Awkward Silence Portion" of the debate, Zim is shown without contacts, despite having them before and after the scene.