Plot hole: When Scott Tenorman shows the other kids a video of Cartman doing his "piggy" act, the angle of the video shot shows that it could only have been taken from the place where Scott was standing when Cartman originally did it - but Scott is seen at that time to have no video camera or any way to have recorded this.
Plot hole: How was Cartman able to afford a fairly lengthy TV ad, when he had already spent all his money on the theme park? Cartman took all his money with him to buy the theme park. After buying the park, he runs the TV ad mocking Stan and Kyle. Soon after, when he hires the security guard, he reiterates that he had spent all his money to purchase the theme park. Cartman would not be able to get a loan (he is too young), even as a co-signer. Cartman's mother is also not wealthy enough to give him the money.
Plot hole: Stan's grandad submits the video of Kenny being hit by the train. This gets through into the final, which shocks Stan and Kyle. But shortly the clip would have had to get through to the final by another episode, so shortly Stan and Kyle wouldn't have been so surprised. The video couldn't have been submitted before, as Stans video was submitted first.
Plot hole: Mr Mackay says he has been working hard on the tooth decay play for 6 years. When he says why it's so important to him, he says it is because it took his father 2 years ago. The monologue exaggerates the length of time he's spent working on the play by saying it was a long time, and exaggerates how hurt he still is that his father was lost by saying it was quite recent. Perhaps the two numbers were stated the wrong way around. (00:15:35 - 00:16:45)
Plot hole: When Cartman is 'confessing his love' to Kyle at the basketball game, the crowd all turn to Kyle and say "Awww" to him. By the time the crowd turn to Kyle, all Cartman had said was that he loves Kyle. No image or live footage of Kyle was ever shown by that point, so how would anyone in the crowd have known who Kyle was or where he was even sitting?