Okay, and this is--"

"A water balloon."

"Colonel Sheppard! You're not helping, you know."

"Okay, okay. Sorry." John crossed his arms, looking entirely unrepentant.

Carson cleared his throat. "These are called condoms," he said carefully, doing his best to avoid meeting anyone's eyes. "They're very effective for preventing the spread of disease. And pregnancy, of course."

"They're effective for pregnancy?" This from Ronon, who'd been busying himself with building a fort out of tampons. No one wanted to be the one to explain to him what they were actually for.

"No, they help prevent it." Carson cleared his throat again. At this rate, he'd be hoarse within the hour. "They're made of latex, and--"

"Why would you deliberately try to prevent pregnancy? Children are a gift." Teyla frowned, looking from Carson to John and back again.

"Not where I come from," Rodney muttered, slouching down in his seat to avoid Teyla's glare.

"Well, where iwe/i come from," John said carefully, making sure his elbow connected with Rodney's side, "There's a lot of people, and not as much space as there used to be. So we want to make sure that people who don't want kids don't have to worry about...accidents."

"If they don't want kids, why don't they just not have sex?" Ronon shrugged, his movement nearly causing the tampon-fort to collapse.

Rodney raised a finger. "Ah. Easier said than done. Much, much easier."

"It's just in case of--accidents," Carson said lamely.

Teyla's frown deepened. "Finding oneself with child should not be considered an 'accident'. It should be a blessing."

"It is! Of course it is!" John's voice was weak and not at all reassuring. "It's...great. Supposedly. I wouldn't know anything about it."

"Not for lack of trying."

"Shut up, Rodney."

"I'm just saying!" Rodney ticked off a finger. "That story you told me about the threesome you had your freshman year." Another finger. "And let's not forget the twins you had your sophomore year." A third finger. "And don't even get me started on your adventures in this galaxy."

If she wasn't careful, Teyla's face would freeze that way. "Shut up, Rodney," John hissed, adding a kick to the shin for good measure.

Rodney's girly shriek of outrage almost drowned out Elizabeth's knock. "Is everything...okay in here?"

"Yes! Yes, everything's fine," Carson said quickly. "Actually, you have perfect timing--I was just trying to explain contraceptives to Teyla--you know, their--uh, their cultural significance and those--things, and I thought you might--"

"What's that?" Elizabeth said loudly, backing towards the door. She put a hand to her ear, mouthing "headset" and "important". They could hear her footsteps echoing down the hallway.

"That sounds a lot like running," John said idly, flicking condoms at Ronon's tampon fort.

"You still haven't explained how these things work," Ronon complained.

"I think this is the part where Carson gets a banana," Rodney offered. "Do we have anything that looks like a banana?"

Carson just sighed.