What letter is this?

I don't know exactly why this cracked me up so much, but it did:

Mom and her daughter (4-5 years old) were reading an alphabet book together.  Mom pointed to the big letter S on the page and asked her daughter, "What letter is that?"  Daughter's response:  "Two!"

I guess I can see how the letter S and the number 2 look pretty similar.  But numbers and letters are not the same thing...