Saturday the 14th (1981, Howard R. Cohen)
Sometimes it's best not to fuck with nostalgia. I saw Saturday the 14th at my grandma's house in the mid-80s, when we used to watch the Saturday Afternoon Shockers. Good times! Anyway, I haven't seen the movie since that day, when I was too young to understand what "spoof" means. I remember actually being scared by a few key scenes. I also recall the TV spot, which went featured a tagline along the lines of "Friday the 13th is bad...Saturday the 14th is worse!" Oh, never has a movie tagline been more literal!
The plot concerns a couple, Mary and John (Paula Prentiss and Richard Benjamin), who manage to beat out their crazy relatives (referred to throughout the film as The Relatives) for an inheritance. They're excited to hear they're getting a house, a little bummed when the will explicitly states that the house is cursed. Still they're happy to move in, even though their kids think it's a bad idea. Lil' Billy finds an Evil Book that says "No really, don't open this book," opens it, somehow misplaces the book, and soon a variety of monsters is roaming the halls. Throw in a couple of bickering vampires (Jeffrey Tambor and Nancy Lee Andrews) perched outside, thinking the house should be theirs. An original enough plot for a movie that's trying to be a spoof, right?