!The Headmaster is a vampire.
Terrence Hardiman's prominent canines, the Headmaster's clear OCD and his hypnotic abilities all fit.


[[WMG: The members of Splat are part of the Headmaster's race]]
this is assuming that the Headmaster is an alien, it could also explain why they are immune to the hypnotism.

[[WMG: Rose was subjected to MoreThanMindControl by the Headmaster.]]


[[WMG: The Headmaster is just a normal human being who happens to have hypnotic powers.]]