Similar situation in ways. On a bench out front of my school (I was an outcast, many people who knew of my existence at the time would say I was scary/creepy or just flat out intimidating). But 3 people burst out the front doors, laughing hysterically, and being roudy.

Without hesitation, the boy and two girls sat on the same bench (it was closest to the door I guess, but there were so many other benches, and they were so small, I just kinda froze). The boy started fake complaining about how tired he was and asked one of the girls if he could lay on her lap. To which she shoved him off the bench. In mock sad face he complained and shoved her playfully back. As I said the benches were small, and though I was still in shock, their roudiness was extremely interesting, and I was used to being avoided like the plague, more than simply ignored... And they just didn't have boundaries with each other and it was amazing to me at the time (very strict religious area, you simply weren't allowed to be that close to the opposite sex). Finally the guy looked at me and just said "Hi! Can I lay on your lap?" I was so dumb founded, I just shrugged. And I'll be damned if he didn't scoot over on the grass and lean his head on my knees. He was still sort of wrestling with the girls (who started talking to me playfully as well) and then a car pulled up, and just like that they hopped up, went to the car, and were gone. I realized I was smiling, and it was just such a crazy shift in my mentality that I sat there another couple hours before finally walking home. I didn't formerly meet the guy till like 2 years later. He didn't remember me I'm sure, but 15 years later, we're still friends, and I'm sure he has no idea he and his friends saved my life that day.