Facepunked
Stealing someone's online account and making them look like a fool by sending out stupid or gross stuff from their own phone.
Your teacher's account sends out a message: 'I just told the principal I'm quitting because of the smell of the copy machine.'
Your friend's mom posts a picture of her wearing a unicorn costume at the grocery store.
Your crush's account sends a DM to your best friend: 'I have a crush on your friend. Also, I hate your life.'