Got this idea from a cute little fan art

Stiles looked at Derek thinking, planing. I wonder if he'll act like a dog. He thought. Slowly he raised his hand and said, "I wonder if I caress," He put his hand on Derek's head. "Here." Derek growled as Stiles touched his head.

Stiles smiled and watched as Derek gave him the side eye. "Stiles stop." But he didn't, Stiles kept caressing Derek's head smiling as he did. He knew it was pissing him off. Stiles liked it.

Derek's teeth sharpened and his claws came out. "What are you doing!" Derek yelled getting in Stiles' face. Stiles smirked and said, "behind the ears maybe." He started to scratch behind Derek's ears.

Derek's face changed from anger to pure surprise and pleasure. He fell forward his head in the crook of Stiles' neck.

His breathing came out in sharp deep breaths. "Don't stop." He whispered. Stiles smiled and thought, Yep like a dog.

Where's the Tail

Stiles smiled as Derek held him to the wall. His lips perfect on Derek's. Stiles slowly slid his hands down Derek's bare chest and to his back. Slipping them into his pants.

Derek jumped and pulled away a little. "Stiles what are-" Derek stopped and looked into Stiles' eyes.

Love and lust filled them and Derek went back to kissing him. That's is until Stiles said, "where's the tail wolfy?" Derek growled and pulled away.

"Really Stiles? Really?" Stiles nodded pulling Derek in for another kiss, filled with love for one another.