My sister had invited her whole class over to our house on her sixth birthday, and since her birthday falls one week before Halloween, the party was Halloween-themed. I was in fourth grade at the time, and we were going to play the SpongeBob Halloween episode to entertain the fifteen kindergartners, but my parents didn't want to show it because they thought it was too scary. Well, not necessarily too scary, but SpongeBob's de-fleshing (?) at the end, when his bare brain is shown is sort of creepy. I was never specifically forbade from watching a certain cartoon, though. Almost understandable, since most of them were five year olds.
You know, my mom knew quite a few other parents who didn't allow their kids to watch SpongeBob SquarePants. They thought it was "bad for the brain" or something.