Near the beginning (if it wasn’t the beginning itself) of this color movie, I remember an elderly woman who eats candy all the time (it’s everywhere in her house) accidentally getting shipped a box that contains a brown haired boy who has been put into stasis. She’s told by the box’s audio instructions to pour an included pouch of liquid into the box (or maybe on the boy), which wakes up the boy. He doesn’t have the flaws associated with children — like wanting to eat candy all the time — and also can do instant multiplication of large numbers.
Somehow the woman and the boy come across and join forces with an elderly man who accidentally received a “perfect” girl (blonde).
A bit fuzzy on the climactic sequence. Somehow they all end up in the lab/factory, I think separated from the boy. There’s a scene where all four of our protagonists, the couple who actually ordered the boy and the head of the lab/factory are all in one room. (I think this is where it’s discovered he can’t do math instantly in his head anymore, though I wonder if that actually happened while he was separated?) The couple (the wife at least) expect the boy to just run up to them, even though they were strangers.
I don’t think the movie has a sad ending — it was probably a family movie.