Just showed this to my kids and they loved it. However I think this was the first time they were ever exposed to the 'get out here we don't want you any more' trope and that scene upset them quite a bit.
Harry was played by Kevin Peter Hall who also played the Predator.
This, like some other 1980s sci-fi/fantasy movies, was originally intended to be a half-hour episode of "Amazing Stories," an anthology series produced by Steven Spielberg. Others included "Back to the Future" and "Batteries Not Included."
There was an episode of amazing stories I had to look up called 'Thanksgiving' where this farmer's well collapses and in the hole is this voice that the daughter starts trading letters with and feeding and it scared the everliving shit out of me as a kid.
Doesn't seem to be on youtube but thanks for reminding me of a buried childhood trauma, I'll have to go digging for a copy.