Dean never really ever got the chance to celebrate his birthday and that is why you decorated the motel room you both were in. The moment he walked in you shouted "Suprise!! Happy birthday"

Dean froze, turning to stare back at you with a look of shock. Then he realized.

"What the hell" He exclaimed, his eyes wide as he saw the decorations, the little cake you'd gotten for him.

"I...you did all this? For me?" He asked, cracking out a smile as he clapped his hands together.