This pseudo-sequel to the original 'Prom Night' (it was completed before the studio bought it and repurposed it as a sequel), has some interesting elements to it - but for a small budget production, it bites off way more than it can chew.
After a freak accident caused by the malfeasance of two men at their 1957 prom causes the sultry Mary Lou to perish in flames, she returns 30 years later to wreak havoc upon those who wronged her, (and everyone else, it seems). While the film seems to dance around some interesting, important subjects, (consent, women's reproductive rights, feminism, maturity, and whether past wrongdoings can ever be forgiven), it always veers into violence, sexual exploitation or schlock before anything of substance can be said. Where 'A Nightmare on Elm Street' had a killer premise and amazing FX to back it up, "Halloween" had something to say about female independence and blind rage, and a variety of other horror films from the Slasher era had some element of social commentary, 'Prom Night II' chooses to ignore all of that for cheap thrills.
Still, there's some classic z-grade cheesy horror films that are enjoyable because of their all out craziness or commitment to their premise. The original Friday the 13th was an example of such a film. 'Prom Night II" could have been similar, but it's absolutely awful direction, aimless, overlong script, choppy editing, and mind-numbing, local-access channel level cinematography suck almost all the enjoyment out of the film.
The only shining element in what is otherwise a turd diamond of a film, is the acting. Michael Ironside, always game to play a sneering villain or misguided patriarch is in fine form, and the young actors and actresses give it their all in thankless roles. Lisa Schrage, as the titular Mary Lou has enough charisma and cunning to pull off a horror villain, (although, the reason why she's a villain is never really apparent - she really just seems like a victim at the end of the day), and Wendy Lyon does a decent job of playing both a puritanical Vicki and a hedonistic Mary Lou. Without the performances to carry the film over, a few, unexpectedly offensive and hilarious jokes, and a few interesting FX set pieces, the film would be unwatchable. It's definitely in the slasher film canon, but it's one of the least interesting films of the genre. Interesting only for slasher completionists or Canadian low-budget film aficionados. It doesn't even reach the level of 'so bad it's good'. 'Hello Mary Lou: Prom Night II', is just kinda boring.