A/N: I was playing around with my nephew and this just...popped into my head. I have no idea why.
Word Count: 487

"Dammit, Cas!"

The tone of Dean's yell was one of horror and Sam threw open the bathroom door, head whipping around the room to see if his brother was in danger.

"What the hell-"

"Go back to the bathroom, Sam!"

Dean stood on one side of the motel room and Castiel on the other, his brother's face scarlet and angry while the angel was passive and inquisitive as always. Dean held the front of his shirt down, knuckles white and fingers fisted in the material. Sam looked from one man to the other.

"What's going on?"

"I don't want to talk about it!" snapped Dean.

"I was attempting to cheer your brother up," said Castiel, ignoring Dean angry response.

"Well, you didn't!"

Castiel looked at him and shrugged. "Obviously."

"Okay, what exactly did you do?" asked Sam, raising an eyebrow curiously.

Dean pointed at the angel. "You just shut u-"

"I blew on his stomach."

A moment's heartbeat passed before Sam broke down into laugher, receiving an angry glare from Dean.

"It's not funny!"

"Dude, it so is!" said Sam, turning toward the angel. "Cas, why would you do that?"

"I observed a mother performing the act on her infant in the park the other day. The child was most upset before she did that, and then proceeded to laugh each time she did it." Castiel looked at Dean innocently. "Your brother was sulking; I thought the act might cheer him up as well."

Sam snorted a laugh. "Dean, how the hell did he get that close to you in the first place?" he asked.

Dean kept his hands tight on his shirt and looked warily at Castiel. "He's fast," he muttered, as if it explained everything.

"You didn't notice an angel's face coming toward your stomach?"

"Look, this is-he's freaking-you know what he's like! All creepy-stealthy silent ninja angel!"

Sam shook his head and laughed. "Relax, man."

"He blew a raspberry on my stomach!" yelled Dean, a hysterical note in his voice.

Castiel furrowed his brow and shook his head in disagreement. "There was no fruit involved."

"It wasn't a raspberry; a raspberry's an insult," said Sam. "A raspberry's just-" Dean watched his brother stick his tongue between his lips and make a farting sound "-that. Cas gave you a zrbtt."

"This isn't an episode of The Cosby Show, Sam!" growled Dean. "A freakin' angel of the Lord just put his mouth-he just-" Dean huffed and shifted on his feet, then pointed to Castiel again and shook his finger. "Don't do it again!"

"What is a 'zrbtt'?" Castiel asked Sam curiously.

"You put your lips on someone's cheek or stomach and blow," explained Sam. "It's like the opposite of a raspberry – it's a sign of affection."

"Ah, then that is what I did," said Castiel, nodding.

Dean's face burned a deeper shade of red and he stalked off to the bathroom.

"I feel violated," he mumbled.