Guinea Pig

James was sprawled on his bed, checking his letter to Lily for mistakes. Sirius stepped out of the bathroom.

"Can I borrow your toothbrush?"

James's head snapped up.

"What? No, that's disgusting. Honestly, Sirius, can't you buy your own?"

Sirius shrugged.

"Can't afford it. So can I?"

James sighed.

"It's 'may I', you Philistine, and why do you want one anyway?"

"I've got a date. I can't show up with my mouth reeking like a Hippogriff's, now can I?"

Sirius was grinning from ear to ear and James snorted. Stretching on the bed, he pulled the drawer of his bedside table open and reached inside it.

"Catch!" he said, throwing something at Sirius, who deftly snatched it. It was a small paper bag bearing an ornate H on one side.

"What's it?" Sirius asked, peering inside the bag.

"Toothflossing Springmints, Honeyduke's latest product. Haven't tried it yet, but given the name, it can only help you."

"Thanks, mate."

Sirius took out what looked like an ice blue string ball and popped it into his mouth. Immediately, his eyes bulged out and he gasped. James observed his reactions with keen interest.

"What does it do?"

Sirius put a hand on his mouth and swallowed.

"Well, it's tooth floss, see?"

"And?"

"And it slithers between your teeth before settling on your tongue. And it's really strong mint. Last time I test something for you, Prongs."

"Well, your teeth are clean now, so what are you complaining about?"

The very picture of wounded dignity, Sirius left the room, only turning at the last minute and sending a pillow onto James's head.