Kiss 'N Tell - S1-E4
Continuity mistake: When Zelda first sees the three headed dragon when it is tormenting the damsel in distress, the surroundings change once she leaps into action and it blows fire at her. The rock the girl is against changes shape, the trees in the background become thicker and more numerous, and the trees and bushes in the foreground change up and in position. (00:01:20 - 00:02:30)