South Park (1997)

Volcano - S1-E2

Plot hole: How could Ned shoot Kenny by accident when he was unable to shoot Scuzzlebutt because he had run out of ammo?

Volcano - S1-E2

Plot hole: Scuzzlebutt is trapped by a river of lava but is able to accept thanks from the Mayor. To do this he would had to have crossed a river of lava.

Ssiscool

Cartman's Mom is a Dirty Slut (1) - S1-E13

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.