Large Dragon at Large - S2-E10
Continuity mistake: As the gang are walking through a market like area, Shaggy says "Like, I can't believe we came all the way to Scotland for a renaissance fair." As he does, the shot changes and suddenly he, Fred, Scooby, and Daphne are looking to their right, when they were all looking straight in the previous shot. The group's arrangement also changes from more scattered, to being in basically a straight line side to side. (00:02:10)
Large Dragon at Large - S2-E10
Continuity mistake: As the dragon begins breaking down the house, the door is green and crumbles. The shot cuts to the two guys screaming and then back to the dragon. Now the broken door is brown. (00:01:55)
It's All Greek to Scooby - S2-E13
Continuity mistake: The gang catches a ride on a boat and have to find room in the animal storage area. Shaggy and Scooby are shown sleeping next to the sheep. But when Lysander walks in, they are next to the goat. (00:10:35)
Large Dragon at Large - S2-E10
Continuity mistake: Lancelot's right glove controlled the dragon, but when Scooby's fooling around with it later it's on his left paw.
Answer: Because of the goo that was on it.