In 1977, the Marauders' prank went too far and destroyed an experiment that Professor Dumbledore was doing, causing all members of Hogwarts and the castle to fall next to Shrek Academy in Douluo Continent.
When the castle is affected by magic and travels back:
James: Blame me?
Lily: Don't you blame the giant squid?
Douluo Zhong: What is a giant squid?
Intention: Intention to be added