Large Dragon at Large - S2-E10
Continuity mistake: After Daphne touches the dragon's tail, Shaggy and Scooby take off and run into one of those coffin like things with spikes on the inside for torture, to hide. As they go in, you can see the spikes on both sides, and there is nothing else in it. But when Shaggy turns on a flashlight, you can see the spikes to their back have vanished, and a skeleton appears. (00:15:50)