This is the episode on the simpsons where Bart wants to become a daredevil. He announces on the bus on a field trip to Springfield Gorge that he will jump it. Finally, on the day of the jump, when Bart finally manages to sneak out of the house, it cuts to a scene of Nelson asking Milhouse, "Where is he? I though he said noon." But you can clearly see that while Nelson is talking, Milhouse's mouth is moving as well...