Growing up, I had the same rubber ducky toy for years. I won it at the local fair by throwing ping-pong balls into fish bowls, and I treasured it like it was a million dollars. I named him Sunny, because he was wearing these cool sunglasses and I was four years old, so my creative ability was somewhat limited.
That rubber ducky stuck around for a long time, and I'm sure my mom still has it somewhere in a box at her house. But as with everything from when we were kids, there are now concerns surrounding rubber duckies, as well as other common bath toys that come in contact with children on a daily basis.
How often are you cleaning your child's bath toys? Probably not frequently, right? It makes sense. Most people assume that if since the toy is already sitting in soapy water, that it's basically clean. Plus, we rarely think about the inside of the toy. The outside is what we see and touch, so why worry about anything else?
That black stuff. That's why.