What a tribute! A mix of Donitz's "Story of the Blanks," http://fav.me/d3kq34i , and Lucio Fulci's 1981 film"The Beyond," one of my all time favourite movies!
Running below we have Ruby and AppleBloom as John and Liza, and Mitta as Schweick's zombi corpse. I was originally gonna put Mitta as the Red one (as she fit Emily's role), but the original poster had yellow eyes so I went with Ruby again.
http://pig-fish.deviantart.com/ helped come up with the "pony-pun" name (Fulci --> Foalci)
Original poster: http://1.bp.blogspot.com/--4QfkE7JKts/T1QgDuJcWFI/AAAAAAAAP_U/JxIrILmDoLw/s1600/beyond_poster_01.jpg
And fitting music: http://www.youtube.com/watch?v=H1pPT-6gFQo
(Also, Lucio Fulci...Lauren Faust...same initials o.o)