WARNINGS: One bad word at the end.
DISCLAIMER: I don't own Teen Wolf and it's characters.
"But what if I do something bad?" Stiles shuddered, pacing around the loft. "Like blow something up? Or turn someone into a monster?"
"Yeah, or you could turn yourself into mermaid," Derek snorted.
"Don't put ideas in my brain," Stiles scoffed, stopping before the werewolf. "Besides it's merman not mermaid for males."
"Whatever," Derek rolled his eyes. "Just calm down. You're doing fine. Besides Deaton told you-" he was cut off by Stiles falling suddenly. Derek caught him quickly, keeping him up by the arms. Stiles blinked up at him in confusion. Derek looked down at him. His eyebrows went high up into his hair line and an amused tilt appeared on his lips.
"I didn't know you actually do that," Derek mused.
"What?" Stiles followed his gaze down and squeaked. He had a tail! Long, bright red tail covered in scales ended with a delicate looking fin. He flailed, causing Derek to encircle his arms around him for a better grip as he almost went down. The boy threw his arms around Derek's neck for support. His tail wrapped itself around werewolf's legs, the fin slapping hard against Derek's calf. Derek made a surprised sound and lost his balance. They fell on the floor. Derek tried not to let Stiles hit the ground too hard, when he fell almost on top on him in his effort to not cause any damage to the fin.
"Are you alright?" the werewolf frowned worriedly at the boy. Stiles nodded, looking kind of dazed.
"Are you breathing alright?" Derek asked. "Do you need water?"
"I have a tail!" Stiles exclaimed incredulously.
"Yes, I noticed. Now answer the questions."
Stiles took a few breaths experimentally, "Breathing seems okay. And no, I don't need water."
"Okay," Derek pulled away and Stiles slipped his arms and tail from around him. The werewolf knelt beside the boy and surveyed him. Stiles looked ridiculous, sprawled out on the floor in his shirts with red tail twitching occasionally at the end instead of legs.
"Oh my God, that's totally your fault!" Stiles groaned throwing one arm across his eyes. He muttered under his breath petulantly, "I should turn you into a puppy for that."
There was a growl beside him. Not deep, big bad wolf growl he usually associated with Derek. No, it was high pitched, like it was made by a very young animal. Dreading of what he would see, Stiles slowly lowered his arm and looked to Derek. Only in the place where the werewolf was seconds ago sat small, black wolf-like puppy. The Derek-puppy had his teeth bared in a snarl and was glaring murderously at him.
"Oh fuck!"