The riddle
How Do You Spell Candy with Two Letters?
Write the answer down
Look closely at the answer, "C and Y". Set out without gaps, it reads c-a-n-d-y. The letter C comes first, the word "and" supplies the middle three letters, and the letter Y finishes the job. The question asks for two letters, and the answer gives two letters with a short word between them.
This one belongs on paper. Said aloud, "C and Y" sounds like "see and why", which is nothing like "candy", so the trick falls flat in the air and lands only when the answer is written or spelled out loud letter by letter.
Why people get stuck
Most listeners hunt for two letters whose names blend into a word. The unspoken rule they set for themselves is that the answer may contain nothing but those two letters. The riddle never states that rule. It allows a joining word, and once that is allowed the puzzle is solved in a moment.
Where candy comes from
The word travelled a long way. It goes back to the Persian and Arabic words for crystallized sugar, and reached English through Old French "sucre candi", meaning candied sugar. English first said "sugar candy", and later shortened it to "candy". The first sense was rock sugar. Only later, mainly in the United States, did it come to mean sweets in general.
A cousin that spells with names
A close relative asks how to spell cow in 13 letters. Both riddles ask for a spelling and answer with something other than the obvious letters.