Sirius removed his trainers and socks first, handing them to Remus. Then he pulled his robe over his head and set that on top of the other items. He noticed the bemused expression on Mr. Potter's face.
"Oy, James, why don't you have a run round the Castle with me?" he joked. For just a moment, he thought that his friend might do it, just for the fun of it, then he seemed to think better of the idea, shaking his head. Sirius didn't have to think hard to imagine why. Lily Evans. He was afraid the prudish redhead would disapprove of such antics.
Good thing Sirius wasn't weighted down by the disapproval of any female.
Now he added his shirt to the growing pile of clothing, all that was left were his trousers. Suddenly he realized that there were more students outside than usual for this time of day. He gave James a suspicious glance. "What, did you tell people?"
"What's a bet worth if someone can't see you've won?" James couldn't help but crack a wide smile at Sirius. He glanced about at the growing throng, mostly of the female persuasion.
"Mr. Black, you're not getting chicken on me, are you?" He began to cluck like a demented hen.
"No, I'm not," Sirius said determinedly, before removing his last article of clothing and handing that to Remus too.