Killer Party (1986) - It's a cross between 'Halloween', 'The Exorcist', and 'Porky's', and it concerns the vengeful spirit of a fraternity pledge killed in a hazing incident on April Fool's Day returning and possessing the body of a sorority girl after another April Fool's prank perpetrated decades after his death pisses him off. Killer Party is so 80's it hurts, and it's somewhat clever in that it has three false starts - a funeral / "dead rising from the grave" scene ends up being a drive-in movie, then a teenage girl watching said movie goes to get popcorn, finds the place oddly vacant, and when she returns to her car is doubly surprised to find that her boyfriend and everyone around her has turned into a zombie, then this scenario ends up being a music video by an obscure hair metal band called "White Sister" (the song is, drum roll..."April You're No Fool").
I love the movie because it manages to escape the undercurrent of misogyny typically leveled against slasher films by focusing on it's three charismatic female leads - and not requesting nudity from either of them, though there is very modest, tokenish nudity from random girls in the first few scenes - it also, and quite obviously, doesn't take itself too seriously. You can't classify it as a horror-comedy (to be honest it's not terribly successful on either front anyway) but it has a nice energy to it, a kind of cute, dumb charm, and it manages to slip in an unexpectedly creepy little ending.
Killer Party also has Ralph Seymour in it, and if cheesy 80's movies are fries, then a Ralph Seymour appearance is fucking ketchup.
Slaughter High (1986) Another maybe, kinda, sorta, less obscure April Fool's themed slasher film starring Caroline Munro, about a nerd, subtely named Marty Rantzen, who is disfigured by acid after a group of bullies set up an April Fool's Day prank and it of course, goes to shit - April Fool's Day also ironically happens to be Marty's birthday. 10 years later, on April Fool's Day, the people who were involved in the prank are invited to a 10 year reunion. They're all surprised to discover that their school is now a spooky, abandoned shithole, and that they're the only people who've even shown up...hmmm? Being that this is a slasher movie, they opt to go in anyway, and when they discover cool beer and other party favors set-up for the taking, they only briefly question the immense weirdness of this situation before they just say "ah, fuck it!" and dig in.
Things, as they are wont to do, begin to go terribly and quite messily awry, and Marty, being a science nerd long before he was a deformed psychopath, proves to be a pretty creative little fucker when it comes to killing these people.
The film has some wide and hilarious lapses in logic, and even when you take the cliched ending into account, all of what came before isn't exactly ruined by it. The kills are pretty decent to pretty brilliant, the acting is uniformly trashy and fun - except for the then 36 year old Munro who seems lost throughout the film - and as mentioned before Marty (donning a creepy Jester's mask ) makes for an effective stalk & slash killer.
As a sidenote, I did learn some time ago that, according to IMDB, Simon "I'm pretty sure this is not my real name" Scuddamore, the actor who portrayed Marty, apparently killed himself shortly after 'Slaughter High' wrapped.
Shame really, because he was actually a lot of fun in this thing.