For reals, I did!
A woman was standing on the corner of a sidewalk next to a busy street. She was holding onto a carriage. As I was walking towards the woman, I saw her turn around to look at something behind and let go of the carriage. The carriage rolled onto the asphalt and stopped a few feet away from the corner.
I rushed over and grabbed the handle of the carriage before it could roll any further. To my surprise, there was an actual baby inside! The baby looked calm, unaware that we were reenacting the opening scene of Ghostbusters 2.
I pulled the carriage back onto the sidewalk towards the woman. She was quite upset with herself and uttered some expletives before she thanked me. I said, "you're welcome," and went on about my business, proud to be a hero, a difference-maker in their lives.
I deserve a cookie.