This happens in the episode where Ralph thinks Ed didn't vote for him for raccon of the year. At the beginnin, Ralph comes in with a vacuum cleaner for Alice. If you watch the background while Ed is trying to plug the vacuum in, you'll notice that the plug falls out of the wall, but as Ed bends over to try and plug it back in, the vacuum has already started. This slip up is easier to see if you use the zoom feature to get a closer look at Ed.