Here is your basic plot of the movie:
(spoilers not included)
So there is this guy who thinks he has come up with a cure for Alzheimer's, but he has to test it on apes first. By coincidence his father (John Lithgow) also has Alzheimer's, this makes him forget he was in Harry and the Hendersons, thus causing him to accept an ape into his home.
I liked this movie a lot, I give it 7.5 out of 10!
On a side note, according to the movie if a monkey has green eyes it means it's smart. So that means I'm a smart monkey too! Yay!