Plot hole: The night of the La Resistance meeting, before Kenny appears as a ghost, Cartman can be seen putting a mirror and a rope into his backpack. These are items that The Mole requested they bring for the rescue operation, but they hadn't met The Mole yet. How did Cartman know what to bring?
Continuity mistake: When Mr. Mackey starts to spin Stan around at the end of the "It's Easy, Mmmkay" song, they spin anti-clockwise. Then, from Stan's point of view, they are spinning clockwise, (the background moves to the left). Then, from Mr. Mackey's point of view, they are spinning anti-clockwise again, (the background moves to the right).
Continuity mistake: After Stan joins back up with the rest of the kids, he finds Eric and Kyle on the battlefield as they are climbing out of the trench. In the first shot of Stan before he speaks, Wendy is clearly standing in front of Gregory on his right and Butters is visible in the second row behind Stan. In the next shot from the side, the kids shift so that they are standing further behind Stan than in the previous shot, Gregory is now standing in front of Wendy on her right and Butters has completely disappeared. In the third shot, a girl in a pink shirt, who was not visible before, is now directly behind Stan and Butters has reappeared.
Continuity mistake: When Mole digs out onto the stage, you can see Terrance and Phillip in their chairs, and the helmets they're wearing have a wire which is connected to the chair. Yet in a closeup of Mole talking to Terrance and Phillip, the wire goes straight up, and isn't connected to the chair.
Continuity mistake: When Saddam is packing his suitcase for Earth, you can see a little doll in the case, on the right hand side of it. But in one shot when Saddam gasps because Satan says he's leaving him, the doll is on the left hand side of the case. Straight after that shot though, it's back on the right hand side of the case.