The little boy's grandfather had taken him for a trip to the zoo and an ice cream. When he came home his mother asked, "Did you thank your grandfather for taking you to the zoo and buying you ice cream?"
The boy didn't answer. She asked again, "I said, did you thank Granddad for taking you to the zoo and buying you ice cream?"
Still no answer. "You answer me, young man! DID YOU THANK YOUR GRANDFATHER?!?"
"Yes," the boy said at last. "Well, why didn't you say so?"
"Because he told me not to mention it!'"