Discord feels Equestria has become a little boring as of late. He feels the need to make life a bit chaotic. Pranks would normally alleviate this but the citizens of Equestria had become accustomed to Discord's antics. A lack of true friends sharing Discord's sense of humor in Equestria compounds his frustration. Another dimension provides the answer to both problems: a hypersonic octopus with a penchant for impossible feats, gossip, and sweets. Korosensei, the unkillable teacher, finds himself roped into Discord's scheme. Equestria is about to get a taste of Mischief from Tartarus infused with not-so-murderous intent and tentacles!
My Little Pony: Friendship is Magic and all affiliated characters belong to Hasbro.
Assassination Classroom belongs to Shueisha and is written by Yuusei Matsui.
Chronologically, this occurs after Make New Friends but Keep Discord/Rainbow Rocks (in MLP:FiM) and the Civil War Arc (in Assassination Classroom).
SPOILER WARNING: This story spoils events past Chapter 100 in Assassination Classroom.
Thanks to hiromiyamoto27 for pre-reading and help with story planning.