When Francine, Arthur, and Muffy first arrive to Prunella's house to ask for another fortune, Francine knocks on the door and is in front of her two friends there. In the next shot after Rubella opens the door and Prunella comes out with her cootie-catcher handy, Francine is behind Arthur and Muffy instead.
In the same scene where Francine, Arthur, and Muffy are at Prunella's house at her front door, when the car in the background is first shown, its headlights are on. When it is shown again, its headlights are off. However, there was nobody in the car to turn the headlights on/off.
At the end of "Mis-fortune Teller", Prunella throws her cootie catcher in the waste basket at Arthur's house - only for his sister D.W. to take it out later that night and use it, and it was damaged when Mrs. Deegan found it in Prunella's laundry after washing. In some later episodes, Prunella occasionally uses it and it is intact.