Mystery at the Lighthouse - S1-E13
Continuity mistake: When the lights in the lighthouse turn on, Pikachu's left ear overlaps Brock's bag despite being behind it. Also, the part of Ash's jacket to the right of his collar goes from white to blue. Additionally, the part of Brock's bag to the left of his head goes from present to absent twice. Furthermore, the keys on the phone go from present to disappearing. Moreover, the right side of the front of Ash's hat goes from being white to being white and red and then back to white. (00:10:08)