So it has been 10 seasons and we STILL haven’t heard Castiel actually laugh, and I think that this needs to happen before the show ends, and that when he does finally laugh for the first time, it has to be because of Dean. That is all. That is all the canon I need. 

After Castiel fell for good, Dean was more than willing to help his best friend learn to live without his grace. Secretly, he even enjoyed teaching Cas all of the mundane human stuff, showing the fallen angel how to adjust to his newfound humanity.

“I don’t know how to dress myself in a way that humans deem acceptable, Dean… I never had to before.” Castiel admitted the first time Dean took him shopping because Cas was going to need a wardrobe of his own from now on.

Dean could barely contain his excitement when instead of having to let Cas shop on his own, he was allowed to help pick out the clothes that he liked on the former angel. Needless to say, if he only picked the shirts that perfectly brought out Cas’ eyes, it was a total coincidence.  

“I don’t know how to prepare human food, Dean… I never had to before.” Castiel said one night when he shuffled into the bunker’s kitchen while Dean was making burgers for the three of them.

Dean immediately invited Cas to help him finish the burgers, and the day after that, he taught Cas how to make breakfast. From there on, Dean taught him something new to cook almost every other day. If Dean kept Cas close to him while doing so, putting a hand on Cas’ hips to guide him, or gently taking Castiel’s wrist to explain to him how something was done, it was a total coincidence.

“I don’t know how to fold laundry, Dean… I never had to before.” Castiel grumbled when Dean walked in on him wrestling with a shirt in the laundry room.

There was no way Dean could hold back his laughter as he saw the flustered look of concentration on Cas’ face, and the adorable way in which Cas wrinkled his nose. If Dean’s brain referred to Cas as ‘adorable’ at least three more times while Dean showed him how to properly fold the laundry, it was a total coincidence.

It was a Saturday night, around midnight, when Dean found Castiel in the library. The fallen angel was curled up in one of the comfortable armchairs, engrossed in a big, dusty book. As Dean watched him and felt the butterflies explode in his stomach, Dean knew that this time, he was the one who needed help. Blue eyes darted up at Dean when he closed the door behind him, and Dean smiled weakly.

“Is everything alright, Dean?” Cas questioned, considerate as always.

Dean nodded as he crossed the distance, tentatively sitting down on one of the arms of the huge leather chair. “Yeah, I’m good… I just need your help with something.”

“Of course, anything.” Cas replied without hesitation, putting down his book. “Just tell me what you need.”

Dean took a deep breath, taking Cas’ hand in a sudden act of bravery, intertwining their fingers and never breaking eye contact.

“I don’t know how to handle falling in love with my best friend, Cas…” Dean whispered, his thumb absently caressing Cas’ knuckles as he quietly confessed his feelings. “I never had to before.”

Cas said nothing at first. Instead, he tugged at Dean’s hand to pull him into his lap, then took Dean’s face in both his hands, making Dean’s heart flail.

“Don’t worry, Dean…” He murmured as he softly, experimentally, kissed the very corner of Dean’s mouth. “I’ll teach you.”