Continuity mistake: In the scene where the Cartman family and boys are seated at table, Kenny sits between Kyle and Great-Grandma. But a few shots later Kyle has to hold Great-Grandma's catheter bag, as he is now sitting next to her, and Kenny is no longer between them. However he's back between them again when the camera shows the whole table.
Continuity mistake: When the town has a Conjoined Twin Myslexia Parade, and Nurse Gollum is walking; you see her right hand down as she walks, and no people in the background. Then the shot changes, and you see her right hand up waving, and people where there weren't any before.