An idea I wanted to share with anyone whose interested. It basically involves combining the episode Castle Mane-ia with Bats!

Basically when the Mane Six enter the old castle, Fluttershy mention's that it's vampire fruit-bat season. While Rarity dismisses this and states that they'll be out before nightfall.

Later on Spike try's to calm his nerves by eating some food he bought along with him, however one of the bat's watching him sees his apple and swoops down towards him. Spike freaks out thinking the bat is after him and flees, Twilight follows them to make sure Spike doesn't get hurt or lost. As the chase continues Spike runs into Fluttershy and Rarity in the halls, Fluttershy the bat chasing Spike and mistakes this for an attack, she quickly uses "The Stare" to subdue the bat while Twilight attempt's to bast it with her magic at the same time, the blast hits the bat and sends it spiraling into Fluttershy, enveloping her in a magic aura as well and knocking her out, the 3 take her back to the library so she can rest.

Unknown to Twilight, accidentally transfers the vampire fruit bats desires into Fluttershy, slowly causing her to transform into a vampire bat-pony hybrid, except she hunger's for blood instead of fruit juice! She quickly flees into the depth's of the castle seeking prey, now the Mane Six must find and capture her before she infects the rest of her friends!

3190338 HOLY EPISODE COMBINATION Darkness Rising!! That's an Awesome Idea!!!

3195889
Interested in trying it out?

3195889 hope it HAPPENDS!!

3195889
I really like this idea! You know what else is a great idea? If Twilight and all her friends actually did get infected and Spike has to save them, since he believes the whole mess is his fault.