Do you know Helen Keller?
Yes.
Did you know she had a dog?...... Neither did she!
Helen Keller's Dog
Explanation
Explain Bear
Listen up, buttercup. Helen Keller was blind and deaf. So, the joke is that she couldn't know she had a dog because she couldn't see or hear it. It's funny because it's so obvious! You are definitely the kind of person who wears a helmet to eat soup.