Three Coaches & a Bobby - S3-E12
Continuity mistake: The two women near Peggy, who are sitting on the benches in the stands, are seated on the fourth and fifth levels in the wideshots, but in the close-up they're seated on the third and fourth levels.
Cartman Gets an Anal Probe - S1-E2
Visible crew/equipment: When Chef is singing: "I'm gonna make love to you, woman!" A crew member's hand can be seen moving the character's head. This was later fixed in the DVD version, but it was not fixed in the original version.
Other mistake: At lunch, when Sam is using a spoon to shape his mashed potatoes on the tray, his right arm clips through the tray just as he says, "Maybe I should clear out the east wall like this." Then, when Sam says, "Maybe I should fortify the south side first," he's using the spoon to move the mashed potatoes on top of the tray, but his arm and spoon are under the tray, so it looks as if the potatoes move on their own. Additionally, when Sam states that he's so confused, the spoon held up in his right hand appears to vanish in the next shot.
Opera House Murder Case: File 2 - S1-E22
Other mistake: At the beginning of the episode, the characters are gathered thinking back about part 1 of the case. Amazingly enough, the propmaster's armpit ate the A of his shirt. Now he's not a "BADMAN", he's a "BADMN." (00:02:05)