Letters Everywhere

Charlie has become fascinated with letters, in a weird way.

When we got into the car this morning he asked for his basketball and once holding it exclaimed: "Oh! All the letters!"

His basketball says "HUFFY SPORTS" in large letters. Charlie pointed to the 'O' in 'SPORT': "Owl!" And then to one of the "F"s in "HUFFY": "Frog!" I cannot for the life of me get him to say the actual letters, as far as he is concerned they are inextricably linked to animals. This leads to conversations like:
CHARLIE: (still holding the basketball) "Where zebra?"
ME: "There aren't any zebras on there, honey."
CHARLIE: "Where hippo?"
ME: "Right there -- H is for Hippo."
CHARLIE: "Where elephant?"
ME: "I don't see an elephant either honey, but there's a snail..."