My son (almost 5) couldn't come up with the word for curtain, so called it a "window blanket"
My daughter (2) was looking at a book of trucks while we were driving in the car. She kept saying "what that? what that?" and pointing at something in the book. As I was driving, I could not see what she was pointing at. I asked my son to help her, and she said "porcupine". Being a book about trucks, I had no idea what she was looking at. My son then pointed out that she was looking at the farm trucks page, and it was a combine harvester.