Cartman Gets an Anal Probe - S1-E2
Continuity mistake: In the classroom there is a poster of The Laughing Cavalier in the back wall in the class. In the last shot of that scene you can notice that the poster has disappeared and is replaced with an astronaut poster. (00:09:05)
Continuity mistake: In the first episode of season 10, when Marissa is holding a dog while talking to Elaine, the way her arm lies around the dog's neck changes several times between shots.
Continuity mistake: When Sheila Carlisle has hanged the dead head up on the wall of Eugene's office, they are all looking at it and the eyes are looking straight in to the room. Later in the episode, the eyes are looking more to the right.
Continuity mistake: When we first see Darren's sister coming out of the apartment she has a pram with her, but there's no baby in it, but in the next shot were we see her go back inside and up the stairs she is carrying her baby.
Continuity mistake: The fish that Harley uses to protect herself from the Joker changes shape and size every shot.