Not my kids, I was babysitting, but I thought I would share anyway.

I was babysitting for a family member, who had two boys. One 3 and one 4. They are playing and I'm sitting nearby watching them and reading a book. I'm literally like 10 feet away from them, in the same room.

All of a sudden the 3 year old screams like he's in pain, gets up, and starts running to me. As he's running, he yells (name changed) "BOBBY BIT MY PENIS!!!"

When he gets to me he showed me his finger, which had a tooth mark in it. Also, both boys were completely clothed.

When their parents got home I told them about it, and they both laughed, and said that the 3 year old had heard the word penis but isn't quite understanding what it means. So he just randomly uses the word.