AN: I don't own Harry Potter or Fantastic beasts. I came up with this today in a weird fit of inspiration.
Harry Potter was dreading his second potions class of first year. The morning started off on a stormy and gloomy Wednesday, giving Harry a foreboding feeling of the class to come. The worst thing about this only being the first week of school was that his magic was still suppressing the painful injuries inflicted on him the night before the Hogwarts Express had left king's cross station. He walked into the potions classroom quietly, not looking up at the terrifying professor Snape. He quite reminded him of his uncle Vernon. As he took his seat, Draco Malfoy gave him a harsh glare. He supposed Malfoy was still thinking about his back talking professor Snape in the first class of the year.
As Harry began the wart curing potion, he nervously kept looking up at the glaring potions professor as he stalked the desks, daring someone to make a mistake. Harry was finely chopping the frog legs when Draco threw something in his cauldron. The other students noticed and took a step back, when the potion exploded and splashed on Harry. As every eye in the classroom turned to stare at the boy who lived, Harry screamed as his bones started to shrink to the size of an infant. The next moment was chaos. With a flash of green light, the now toddler Harry Potter vanished, never to be seen again, or so everyone thought at the time.