It was Sam's birthday soon and Dean and Cas wanted to do something special for him since it's been almost a year since anyone has died , which happens rarely.

"So Cas, what do you think we should do for him?"

"Have a party? Isn't that what humans do?"

"Yeah exept tiny problem, all our friends are dead."

"We could have a party with just the three of us though. "

"Then it wouldn't be a party, Cas"
It's been almost two years that Cas has been living with us and he still doesn't understand humanity. Dean though as he watched the angel's face tilt in confusion. 

Then, Dean had an idea.

"What if we make him a cake?"

"Dean, I can't cook."

"Good thing that I can."

While Sam was out with his boyfriend Gabe, Cas and Dean started putting together the ingredients for the cake.

"Cas have you seen the flour?" He looks over to where he last saw Cas but he isn't there anymore.

"Cas?"

He walks across the kitchen and peeks into the living room,  where is he?  Then, as he walks back into the kitchen he is met with a shower of flour. He opens his eyes but some flour gets in his eyes. He rubs his eyes and shakes some flour off his hair and shirt. When he can finally see, he sees a grinning Cas holding an empty packet of flour in his hand.

"Oh so you think it's funny?"

Dean says as Cas goes into a laughing fit.

"You look like a-"

He didn't understand what the last thing that he said was and when he asked Cas respoded with "It's funnier in enochian."

Dean helped Cas clean up the mess and because he couldn't be bothered changing shirts, he took his off. Dean hasn't noticed but Cas has been staring at his body, checking him out and looking at places he provably shouldn't be looking but he couldn't help himself. He put the cake into the oven and Dean said to wait for 40 minutes. When it was done, they started decorating it.

"Can you write something on the cake while I go ask Sammy when he's coming?"

"Okay."

Cas didn't know what to write and after Dean left to call his brother, he wrote the only thing he could think of. After he put the writing on the cake he decided to add a bit more flavour into the cake since it looked too plain to him. He took some ingredients out of the fridge and stuffed them into the cake. Dean rushed in after Cas has finished redecorating and said that Sam is at the door, Dean didn't even look at the cake. Cas took it and put it on the table in the living room and when Sam and Gabriel came in, the burst out laughing.

"I-i don't understand why you are laughing. "

Dean was the one to answer.

"Cas when I told you to write something on the cake I meant something like 'Happy birthday Sam'."

"Oh...I'm sorry."

He looked apologetically to Dean. He had written on the cake 'It is your birthday'.

"Okay so let's try it!" Sam said, ignoring the writing. He took a knife from the kitchen, cut a slice and put it in his mouth.

"Nice, what's in there?"

Dean started listing the ingredients.

"Chocolate, vanilla, coconut sprinkles-"

He was interrupted by Cas who listed more ingredients.

"Strawberries, fish, onion, pickles and orange."

Sam immediately spit it out back into the plate and Gabe and Dean started laughing.

"Was it the orange? Do people not put oranges in cakes?"

Cas tried to understand what he did wrong.

"No Cas...you don't put pickles or fish into a cake."

"Oh...again, I'm very sorry."

"It's okay Cas, I think today is one of the best birthdays I've had."

Gabe leaned in and softly kissed Sam on the lips.

"Happy birthday Samoose."