Creepschool is a Swedish, French and Canadian series about four kids who find themselves at a strange boarding school.
Tropes in this series include:
Be Careful What You Wish For: One episode has Janice annoyed with everyone and wishing they'd leave her alone, which results in her being trapped in an alternate version of the school where no one else is around. While she enjoys it at first, she soon starts feeling lonely.
Becoming the Costume: The Halloween episode had this happen to the four main characters. Also, see "Demonic Possession" below.
Demonic Possession: One episode has six of the students be possessed by six characters from a book they'd accidentally selected to do a play on not knowing that the characters in the book had been imprisoned in it.
Fountain of Youth: Happens to Janice and Victoria in one episode after taking a bite out of a magical fruit that can have strange effects if eaten raw. They keep getting younger, so their classmates must find a way to reverse it.
Halloween Episode: One episode has the four kids deciding to teach the school about Halloween. Turns out, everyone at the school already knew what Halloween was and were just playing along pretending they didn't know so they could pull a joke on the kids and show them their way of celebrating. It also turns out that Halloween was invented by them in order to let the students go out among regular people without drawing attention to themselves.
One episode has Elliot unsure of what his goal in life is, and decides to try out a few goals he comes across in the Chamber of Goals. He later discovers that he has unwittingly been robbing his friends of their dreams, causing them to fade away.
Janice dares Victoria to take a bite of a particular fruit they'd been warned not to eat raw (not having heard the full warning of it having strange effects due to their bickering earlier in the episode), and ends up unwittingly causing both Victoria and herself (as she took a bite of the fruit too after Victoria said it tasted good) to keep getting younger and younger.
One episode has the kids arguing and fighting out of frustration that its been raining for two weeks, and Elsa tries to make the fighting stop by whistling a magical fairy melody she learned from her grandmother that makes people into what you want them to be. It works at first, but when she ends up carelessly singing about how happy she is that "everyone is happy, just like me" to the same tune, she ends up accidentally turning the entire school (except Tony, who was wearing ear plugs at the time) into copies of her.
Nice Job Fixing It, Villain: The episode which has the kids get possessed by the characters in a play they were rehearsing, has the character possessing Victoria being a writer who is having difficulty coming up with an ending for the story he is writing. The evil witch possessing Elsa at one point mentions that they should get rid of said character once she has gotten her revenge, since said character managed to get them all stuck in the book the last time they escaped. When the witch is having the writer trap Malcolm and the teachers of the school in the book, Dorothy finally figures out how to stop them based on what Malcolm wrote about the last time this happened, and asks the writer about how they think a good story usually ends. They decide to write a happy ending in which everything returns to normal, much to the witch's dismay.
Now Do It Again Backwards: After a magical fairy song Elsa was taught by her grandmother accidentally turns everyone in the school (except Tony) into copies of her, Elsa eventually realizes she can reverse the effect by whistling the song backwards.
Stable Time Loop: One episode has Janice repeatedly travel back in time to help a young boy, who at the end is revealed to have been the principal Malcolm when he was younger, and her time travelling led to Malcolm ending up in the care of Mr. Mars, who founded Creep School.