Fluttershy woke up to Rainbow Dash still beside her with her hooves around her. The sun was visible through her window. She gave a tiny gasp and quickly turned over.
"Rainbow!" She poked Rainbow Dash. "Rainbow, wake up! You forgot to stop the storm with the other pegasi!" Fluttershy's yelling wasn't very loud, but it was loud enough to wake up Rainbow Dash.
"Calm down Fluttershy, that was hours ago. I didn't miss it." Rainbow yawned. Fluttershy looked close enough to notice two of her teeth and turned into fangs.
"Oh no," she said quietly. "No…" She lowered her head a little.
"What was that Fluttershy?" Rainbow Dash got out of the bed and walked over to the window where Fluttershy was also headed to.
"Oh, nothing. Just talking to myself." Fluttershy yawned a little, but just enough to notice Fluttershy had two fangs.
"Um, Fluttershy, what's wrong with your teeth? It kinda looks like you have…. Fangs." Rainbow Dash took a tiny step back.
Fluttershy quickly closed her mouth. "I…. I…." Fluttershy knew she couldn't escape this one. She lowered her head and sighed. "You know how a while ago, when I turned into a vampire fruit bat?"
"Yeah! It was so cool how you had fangs and bat wings and-"
"Well," Fluttershy interrupted, holding up a hoof for Rainbow to stop. "Whenever night comes, I kinda turn into a bat and can't really control what I do when I see a pony. That's why I didn't want to sleep with you. When I bite ponies, they usually die…" Fluttershy paused, sick with the thought she sometimes kills innocent ponies. "But that's not what happened to you." She looked back up to Rainbow's shocked face.
"So… What did happen to me?" Rainbow Dash asked, following Fluttershy and went to her bathroom.
"Just take a look at yourself, Rainbow. Just look." Fluttershy turned away, willing herself not cry.
"I don't see any-" That's when Rainbow Dash noticed her fangs. She got closer to inspect them. "Woah.." Rainbow Dash marveled at her newfound fangs. "Did anything else change?" she asked, turning towards Fluttershy.
"Yeah," she squeaked. "Look at your cutie mark." Rainbow turned and looked at her cutie mark. It was like her old one, but instead of a cloud, it was a bat.
"This. Is. Awesome! I can't believe I turned into a bat like you!" Rainbow jumped up and down and small circles.
"Well, only at night. And you can't really control what you do to other ponies." Fluttershy noticed how excited Rainbow Dash was. "But wait, how did I become like this?" She looked over at Fluttershy, confused.
"I guess at some point in the night, most likely when I first turned into a bat and saw you, I bite you in a different place than normal. So I guess instead of dying, you turned into a bat like me." Fluttershy started walking out of the bathroom and downstairs to start making breakfast. Rainbow followed, filled with questions she wanted answers to.
"Then how come when I woke up and it was still night I didn't turn full-bat?"
"Maybe because I had just bitten you, the effects of it didn't start."
"Is that why you weren't there when I woke up to take care of the storm?"
"Yes."
"What were you doing?"
"I was sucking the juice of apples and spitting the seeds. I made sure they weren't Applejack's though."
Rainbow Dash opened her wings to see if they changed. To her delight and surprise, they had changed into bat wings. Fluttershy went into the kitchen, unaware of Rainbow's wings. Fluttershy started on making eggs. When they were ready, she placed plates on the table. Rainbow Dash hungrily ate the eggs and was finished before Fluttershy took a bite out of hers.
Rainbow leaned back in her chair and put her hooves behind her head. She stuck out her wings and said, "These babies changed too." Fluttershy looked over and Rainbow Dash and stared open mouthed at her bat wings. "And it looks like yours changed too." Fluttershy looked at her own wings with surprise.
"I guess it's becoming more permanent every time." She gasped. "What are we going to tell the others? They can't see us like this with our bat wings!" Fluttershy got up ignoring her eggs and started running around her house. Rainbow got up and stopped her.
"Let's go to Twilight's house and tell her what happened. With you being a bat and biting me and all." Rainbow Dash blushed a little. "Then we can go to Rarity's so she can help us cover up our wings and cutie marks."
"But, what are we gonna do until we get there?" Fluttershy started breathing harder and harder.
"Calm down Fluttershy. We can just fly high enough so nopony sees us." Rainbow headed for the door, gesturing for Fluttershy to follow. Fluttershy followed. Rainbow opened the door and took to air, with Fluttershy close behind.