Ms. Grunkle frequently appears to taunt you. She can show up anywhere...
What happens if you don't talk to Madame Pomreda and do an activity anyways? Her eyes appear in front of you and say "Come to Madame Pomredas to accept your challenge!"
Repsac. Just...Repsac. He is heavily implied to be The Dragon to Ms. Grunkle. His sole purpose in the game? To hop out in front of you when you least expect it and ask you a question. Get it wrong? Then you lose health. Lose enough? You go to the labyrinth. Oh, and he'll jump you inside the Labyrinth, too - so no luck hiding in there.
The Labyrinth. There is no real sound there, apart from the background music. Nothing Is Scarier....
The boat sequence can be scary if you have a slow computer...meaning you go forever.
Madame Pomerada herself is pretty creepy especially when you first meet her it seems fine at first untill she lifts the curtain to reveal her creepy Uncanny-looking face.
Fridge Horror: You missed a day of class, thankfully the one where your classmates are turned into monster. Consider the Adult Fear their parents were going through.
Forget that, consider what your parents would be going through!