Sam opened the door, balancing a box of donuts on his arm. He held it open briefly for Dean before entering the apartment.

"What about those-" He stopped, both verbally and physically. So suddenly that Dean walked directly into the taller man's back.

"What the hell?" Dean said, stepping back and rubbing his face. He stopped too, staring. "Oh, jeez. What the hell."

Castiel was sat in the middle of the floor surrounded by bubble wrap. He looked incredibly intrigued and confused, picking up sections and raising his dark eyebrows slightly when a plastic bubble popped.

"Cas," Dean said slowly, "what are you doing?"

The angel looked up at them, brow furrowed. He gestured at the bubble wrap around himself.

"This is … fascinating," he replied, picking up another plastic sheet and popping three bubbles with his thumbs. Castiel inspected the empty bubbles closely before popping some more, looking slightly less confused and more interested.

Sam covered his mouth to hide a smile, walking past the angel to put the donuts on a table, trying not to laugh. Dean sighed and sat next to Castiel, resting his elbows on his knees.

"This here, Cas, is bubble wrap," he told the angel, like an adult explaining to a child. Castiel looked at Dean and cocked his head slightly.

"Bubble wrap?" he repeated, looking back down at the plastic wrap. He held a piece up to his eye level, examining it. Dean grabbed it off him and held it out.

"See," he explained. "These are like tiny air cushions. They're used for packaging breakable things."

Dean popped a few of the little plastic bubbles loudly, smiling at Castiel's surprised expression.

Sam watched the two, grinning to himself as he opened the box of donuts.

"Next he'll be after styrofoam," he laughed, half to himself and half to Dean, but his brother was also distracted by the bubble wrap now, much like the angel beside him. Sam shook his head, smiling, before going and sitting down with them, grabbing his own piece of bubble wrap.

"Okay, then," he exclaimed, "let's see who can pop the most bubbles in ten seconds."