Seemingly Senile Grandpa Saves Teenage Boy (Eddie) From Crazy Family

by Chris
(Virginia, USA)

Please help me identify this crazy late 80's or early 90's horror comedy about a young man (Eddie I think) whose family is either possessed by evil beings or just deranged.

His grandfather also lives with them, but he is senile. After everyone in the family (except grandpa) is possessed, they start behaving very strangely and speak in repetitive chants.

At one point, mom and dad are in the kitchen, and mom is chanting 'Something's got to be done, love him as much as you do,' and dad is chanting 'I know, we'll kill Eddie!' over and over and over.

Eddie eventually realizes that Grandpa isn't as old and useless as everyone thinks, and together they fix it all - I'm not sure how.

That's all I remember. Please help!