LOL! What about a melon Hachiko?
Until some samurai girl tried to split the melon! Okay, I can totes see Lulu (AKA Megumin) trying to do that with her broom after she hears about the popular Japanese summer vacation tradition from Jade, and Hachiko going "Ruh-Roh!" before hightailing it outta there at rocket dog speed. Hmm, beach party episode idea? Feel free to use it!
Actually, a Scooby Doo-esque quest would be cool, with the students working with a detective witch and her K9 Buffy McScruffy to solve a mystery. Maybe to find illegally harvested Fairy Dust and Pixie Powder?
Uhh, magic drugs are BAD, mmkay witches?
Stay in school and don't do drugs, witches!