Sam was worried about Dean. It's not just that he had been turned into a five year old. It was that he was acting like no one his age had a right to. Dean would flinch when anyone moved suddenly or there was a loud noise. He didn't talk, he wouldn't ask for anything verbally or otherwise which lead to Sam having to for him to eat and drink and just about everything. Even when he tried to make Dean eat, it wouldn't be much. Sleeping didn't happen often due to nightmares and even smiles were a rarity. Sometimes if he was lucky, Dean would give a half smirk, but he never smiled.
It made Sam realize how much Dean gave up raising him, how much he was responsible for and how much he lost.
So Sam did everything he could to get the little half smirks out of Dean, pie for dessert every day, playing AC/DC, buying toys, making silly faces. It didn't usually help and Sam was out of hope.
But then they stopped by Bobby's. He pulled out an old stuffed teddy bear to give to Dean. He thought that Dean looked grateful but it was hard to tell. Dean slept with it every night.
What changed everything was when Bobby told him what Dean would call the bear. Dean had named it Pala. Like the car that had been his home for his entire life. And it gave Sam an idea.
Deans birthday was only a week away, and he was going to do his best to make him happy dang it.
On the day, there was no party. There was no party because Dean had no friends, and would occasionally have panic attacks if there were too many people. What there was was a lot of pie, hamburgers for dinner, loud music, star wars marathon, and a wrapped package. When he approached it, Dean looked mistrustful. Not a lot in his life had gone well, so he was suspicious of most everything. With an encouraging nod from Sam, he slowly took off the paper.
To find a stuffed impala. He just sat there shocked for a minute, staring at it mutely.
Well this was awkward. Sam had really thought he'd like it. Just as Sam was about to apologize and offer to get Dean something else, Dean grabbed the Impala and hugged it fiercely, face smooched on the hood.
And as the broken boy hugged his gift, a whispered "Thank you Sammy" could be heard. Maybe there was some hope for Dean after all.