One day in school, the teacher decides to play 20 questions.

So the teacher says "OK kids, I am thinking of something round, and red"

Little Suzy pipes up "I know, it's a tomato".

"No but you're thinking, it's an apple" replies the teacher.

So Little Johnny stands up, places his hand in his pocket and says "I am holding onto something that is round, hard, and has a head on it"

"Go to the principals office" says the teacher.

"No but you're thinking", say Johnny, "It's a quarter"