Harry Potter idea,
Severus Snape was busy brewing a new experimental potion to help with 'Longevity', he was just about to add in a very volatile ingredient when a young Draco Malfoy walked into the room, banging the door in the process and startling Severus enough to drop the ingredient. Severus had just enough time to throw Draco out of the room before the potion exploded, leaving Severus as a 6 year old on the floor. Draco could only freak out, grab Severus (causing him slight pain) and run, right into Dahlia Harriet Potter.
Deaged Severus, Fem!Harry, Hufflepuff Harry, Motherly Harry, Snarry fluff, Drarry