"Don't worry Cas, we'll find a way to change him back. I should be able to reverse this."
"CAS!"
"It was just a low level witch. Not even all that powerful really. She just got the drop on us. I'll gather the necessary ingredients and materials, and we'll have Dean fixed up in no time."
"CAS! CAAAAAAAAS!"
"But what do I do?"
"You watch him."
Cas balked. "Me? I don't know anything about taking care of a baby. How am I supposed to protect him?"
Sam paused for a moment; he seemed to think it over. "Ok, yeah. I'll make a list of stuff we need for you, and I'll stay here and watch Dean.
"S'my?" Dean gurgled and smiled. Damn he was a cute kid; it was almost too bad they had to change him back.
Sam wrote out the list of needed items and handed it to Cas. "These are pretty simple, shouldn't be too hard to find."
"Alright, I"ll return shortly." Cas turned to the smiling, squirming baby. "Goodbye Dean."
Dean looked up at him with big, confused green eyes. "Bye bye? Cas bye bye?"
"Yes, I'll be back soon."
Dean began to sniffle. "No. No no Cas." He held up his little hands to the former angel.
"I'm sorry Dean, but I have to leave."
"NO!" Dean hiccuped, tears filling his eyes. "No Cas. No bye bye!" He wiggled his fingers again, trying to reach out for the man.
Cas stepped backwards, away. He knew he had to go. He had to collect the things on the list Sam gave him. He turned around, and opened the door, his heart heavy.
"CAAAAAAS NOOOOO! NO BYE BYE! PEEZE NO BYE BYE!"
Little Dean began to cry in earnest and Cas felt an iron band clench around his chest. Tears filled his own eyes. How could he do this? Adult Dean carried himself with such rigidity, never allowing himself to open up, to ask for what he needed or wanted; but this baby didn't have the same walls or filters. Baby Dean only knew how desperately he did not want Cas to leave him again, so he cried and reached out for him, tried to stop him.
In that moment, God Himself could not have made Cas leave Dean behind again.
He closed the door and turned back around to face little Dean and an increasingly agitated Sam. "Don't cry, Dean. Please don't cry."
"Cas —" Sam began.
"No, Sam. I'll stay here. You can get what we need. It won't take long." Cas reached out and took little Dean in his arms. He wiped the tears off the baby's chubby face and tucked him up onto his shoulder."
"Cas stay?"
"Yes Dean. I'll stay."
"You sure, Cas?" Sam asked, grabbing his coat and the car keys."
Cas looked down at Dean happily snuggling into his shoulder, his little arms wrapped tightly around his neck. He smiled. "Yeah, I'll stay."