Siblings Mimi (Nita-Josee Hanna, outrageously talented), a ferocious force of nature, and her timid older brother Luke (Owen Myre, also terrific) find a strange, glowing gem while messing around in the dirt. Turns out it summons a blue-hued, bad-tempered alien (actor Matthew Ninaber under a ton of makeup and prosthetics) from the planet Gygax; considered a “demon” by his enemies, he describes himself as “the archduke of nightmares”. However, once Mimi works out they can control him with the gem, she renames him Psycho Goreman, or PG for short.

Delighted with this new source of power, Mimi goes on to prove there is truly no force in the universe more capricious, cruel and catty than a 12-year-old who can have anything they want. Soon, she is forcing PG to turn her brother’s friend Alasdair (Scout Flint) into a squat monster that looks like a giant brain with craft-shop googly eyes, as well as compelling everyone to play a ridiculously otiose sport she made up, the rules of which take hours to explain.

Writer-director Steven Kostanski is a wee bit over-reliant on bathos to generate humour; just about every laugh is generated by PG declaiming something menacing or committing an act of violence and then being treated like a naughty puppy by Mimi. Nevertheless, the gag is worked over from enough different angles to keep it funny, and it helps that Hanna, Ninaber and the rest of the cast have acute comic timing and know how to sell the material.

Meanwhile, the makeup effects for PG, Alasdair and a whole menagerie of alien monsters are unnervingly moist and menacing. It’s no surprise to learn Kostanski has worked as a special makeup artist on bigger budget projects such as Suicide Squad and It, but this proves he has a way with actors as much as a knack for latex and fake blood.

• PG: Psycho Goreman is available on Shudder from 20 May.